scholarly journals COMPARATIVE CHARACTERISTICS OF COATINGS WITH SiO AND GeO ON LEUCOSAPPHIRE

2021 ◽  
Vol 26 (2(78)) ◽  
pp. 14-21
Author(s):  
V.F. Zinchenko ◽  
I. R. Magunov ◽  
O. V. Mozkova ◽  
B. A. Gorshtein ◽  
V. P. Sobol’ ◽  
...  
Keyword(s):  
Solid Surface ◽  
Multilayer Coating ◽  
Contact Angles ◽  
Qualitative Assessment ◽  
Condensed State ◽  
Multilayer Coatings ◽  
Gaseous State ◽  
Film Forming ◽  
Spectral Ranges ◽  
First Moment

The reasons for the sharp difference in the adhesion of multilayer coatings containing SiO or GeO together with Ge on a leucosapphire (Al2O3) plate have been established. It should be mentioned that Silicon(II) and Germanium(II) oxides are quite stable in the gaseous state and, contrary, are metastable in condensed state; at high temperature they disproportionate into ultra-dispersed composites of amorphous nature. A comparison is made of the surface properties of ultramicroscopic droplets formed on solid surfaces – a substrate or the previous layer – upon condensation of SiO, GeO, or Ge vapors on leucosapphire. A qualitative assessment of the ratio of the corresponding contact angles of wetting by the indicated melts, formed at the first moment of contact, has been carried out. In assessing the surface tension of SiO and GeO melts (or Si – SiO2 and Ge – GeO2 composites), we proceeded from the corresponding values for SiO2 and GeO2, which are 296 and 248 mJ/m2 near the crystallization temperatures. On this basis, it was established that the smallest value of the contact angle, and hence the best wetting, is observed for the GeO melt (somewhat less for the SiO melt) on the solid surface of Al2O3 or Ge; the solid surface of SiO or GeO (especially, the first of them) with molten germanium should be much weaker wetted. Hence, it follows that thin-film multilayer coatings obtained from Ge and GeO on a leucosapphire substrate should have a significantly higher climatic resistance due to higher adhesion compared to multilayer coatings from SiO and Ge. Indeed, a multilayer coating containing SiO on a leucosapphire substrate with a large surface can withstand storage in air for no more than 2–3 months and begins to peel off; at the same time, the GeO coating remains intact after 4 years of storage. Thus, the GeO film-forming material is a promising one for use in multilayer coatings such as cut-off filters in interference optics of the near and mid-IR spectral ranges.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

Contact Angles and Solid Surface Tensions

2010 ◽  
pp. 491-554 ◽  
Author(s):  
Robert David ◽  
Jan Spelt ◽  
Junfeng Zhang ◽  
Daniel Kwok
Keyword(s):  
Solid Surface ◽  
Contact Angles ◽  
Surface Tensions

scholarly journals Optical fluxes propagation in the planar transport layer of multilayer coatings

2021 ◽  
Vol 2144 (1) ◽  
pp. 012013
Author(s):  
E V Egorov ◽  
V K Egorov
Keyword(s):  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Multilayer Coating ◽  
Transport Layer ◽  
Multilayer Coatings ◽  
Resonance Mechanism ◽  
Layer Width ◽  
Efficiency Comparison ◽  
Resonance Propagation ◽  
Waveguide Resonance

Abstract The article is concerned with peculiarities study of the quasimonochromatic optical fluxes propagation through thin planar transparent layer of multilayer coating. There is shown that these fluxes can be transported by the layer in process of its multiple consequtive total internal reflection or by the waveguide-resonance propagation manner depending on correlation between the layer width and the radiation coherence length half of transported fluxes. Efficiency comparison of these radiation transportation mechanisms showed that the waveguide-resonance propagation approach is more adequate for results description of the optical waveguides functioning. It allowed to conclude that optical waveguides (fibers) function in frame of the waveguide-resonance paradigm and the waveguide-resonance mechanism is responsible for the light fluxes transportation on great distances.

Nanowear of Multilayer [(TiCx/Ti/C)÷a-C]n Coatings

2018 ◽  
Vol 279 ◽  
pp. 153-159 ◽  
Author(s):  
Anna P. Rubshtein ◽  
Alexander B. Vladimirov ◽  
Sergey A. Plotnikov
Keyword(s):  
Wear Rate ◽  
Tool Steel ◽  
Elasticity Modulus ◽  
Multilayer Coating ◽  
Wear Test ◽  
Constant Load ◽  
Multilayer Coatings ◽  
Diamond Indenter ◽  
Low Wear

Hard multilayer coatings are technologically promising materials for reducing wear of tribological parts. Multilayer coatings with a systematic alternation of the pair [(TiCx/Ti/C)÷(a-C)] were deposited on stainless and tool steel by the PVD technique. Hardness (H), elasticity modulus (E) and critical cracking load (Pcr) were determined by the nanoindentation method. Nanofrictional wear test was conducted under multipass sliding of a diamond indenter (Ø 50 nm) under constant load. The specific coefficient of nanofrictional wear of [(TiCx/Ti/C)÷(a-C)]nwith different composition of titanium-containing layers was determined. The nanofrictional wear rate of [(TiCx/Ti/C)÷a-C]ndepends on the elastic and plastic characteristics of multilayer coating as a whole. Coatings having H3/E2> 0.12 and Pcr> 58 mN demonstrate low wear rate.

Influence of the nanostructure of the functional layers of a multilayer coating on the wear of a carbide tool

2021 ◽  
pp. 332-336
Author(s):  
A.A. Vereshchaka ◽  
V.P. Tabakov
Keyword(s):  
Fracture Resistance ◽  
Crack Formation ◽  
Multilayer Coating ◽  
Multilayer Coatings ◽  
Carbide Tool ◽  
Scratch Testing ◽  
Nanolayer Thickness

The results of studies of the effect of nanolayer thickness on the wear of carbide tools are presented. The effect of nanolayer thicknesses on microhardness and fracture resistance of a multilayer coating during scratch testing is shown. The role of nanostructure in the processes of crack formation in multilayer coatings during cutting is revealed.

scholarly journals Chitosan/Essential Oils Formulations for Potential Use as Wound Dressing: Physical and Antimicrobial Properties

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2223 ◽  
Author(s):  
Elaine Pereira dos Santos ◽  
Pedro Henrique Medeiros Nicácio ◽  
Francivandi Coêlho Barbosa ◽  
Henrique Nunes da Silva ◽  
André Luís Simões Andrade ◽  
...  
Keyword(s):  
Essential Oil ◽  
Antimicrobial Properties ◽  
Wound Dressings ◽  
Qualitative Assessment ◽  
Diffusion Method ◽  
Mechanical Resistance ◽  
Film Forming ◽  
Good Transparency ◽  
The Impact

Film-forming emulsions and films, prepared by incorporating different concentrations of clove essential oil (CEO) and melaleuca essential oil (MEO) into chitosan (CS) were obtained and their properties were evaluated. Film-forming emulsions were characterized in terms of qualitative assessment, hydrogen potential and in vitro antibacterial activity, that was carried by the agar diffusion method, and the growth inhibition effects were tested on the Gram-positive microorganism of Staphylococcus aureus, Gram-negative microorganisms of Escherichia coli, and against isolated fungi such as Candida albicans. In order to study the impact of the incorporation of CEO and MEO into the CS matrix, the appearance and thickness of the films were evaluated. Furthermore, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, a swelling test, scanning electron microscopy and a tensile test were carried out. Results showed that the film-forming emulsions had translucent aspect with cloudy milky appearance and showed antimicrobial properties. The CEO had the highest inhibition against the three strains studied. As regards the films’ properties, the coloration of the films was affected by the type and concentration of bioactive used. The chitosan/CEO films showed an intense yellowish coloration while the chitosan/MEO films presented a slightly yellowish coloration, but in general, all chitosan/EOs films presented good transparency in visible light besides flexibility, mechanical resistance when touched, smaller thicknesses than the dermis and higher wettability than chitosan films, in both distilled water and phosphate-buffered saline (PBS). The interactions between the chitosan and EOs were confirmed by. The chitosan/EOs films presented morphologies with rough appearance and with EOs droplets in varying shapes and sizes, well distributed along the surface of the films, and the tensile properties were compatible to be applied as wound dressings. These results revealed that the CEO and MEO have a good potential to be incorporated into chitosan to make films for wound-healing applications.

Macroscopic Wetting Behavior and a Method for Measuring Contact Angles

1990 ◽  
Vol 112 (3) ◽  
pp. 289-295 ◽  
Author(s):  
K. Katoh ◽  
H. Fujita ◽  
H. Sasaki
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Liquid Surface ◽  
Contact Angles ◽  
Critical Height ◽  
Solid Cone ◽  
Wetting Behavior ◽  
Conventional View ◽  
The Subject ◽  
Thermodynamic Instability

Macroscopic wetting behavior is investigated theoretically from a thermodynamic viewpoint. The axisymmetric liquid meniscus formed under a conical solid surface is chosen as the subject of the theoretical analysis. Using the meniscus configuration obtained by the Laplace equation, the total free energy of the system is calculated. In the case of the half vertical angle of the cone φ = 90 deg (horizontal plate), the system shows thermodynamic instability when the meniscus attaches to the solid surface at the contact angle. This result, unlike the conventional view, agrees well with the practical wetting behavior observed in this study. On the other hand, when 0 deg < φ < 90 deg, the system shows thermodynamic stability at the contact angle. However, when the solid cone is held at a position higher than the critical height from a stationary liquid surface, the system becomes unstable. It is possible to measure the contact angle easily using this unstable phenomenon.

Application of PVD Coatings for Improvement of Die Performance in Copper Semi-Solid Processing

2006 ◽  
Vol 116-117 ◽  
pp. 84-87 ◽  
Author(s):  
Sang Yong Lee ◽  
Sang Yul Lee
Keyword(s):  
High Temperature ◽  
Protective Coatings ◽  
Multilayer Coating ◽  
Multilayer Coatings ◽  
H13 Steel ◽  
Crn Coating ◽  
Aisi H13 ◽  
Improved Performance ◽  
Semi Solid ◽  
Superlattice Period

TiAlN/CrN multilayer coatings with an superlattice period of 6.1nm was applied to a proto-type high temperature segment mold for Cu semi-solid processing so that it was investigated the possibilities of TiAlN/CrN multilayer coating as a candidate protective coatings to extend the lifetime of high temperature molds and dies. Much improved performance was obtained from the TiAlN/CrN coated molds, although different behaviors were observed depending upon the type of substrate mold materials. . Improvement of mold performance was observed by TiAlN/CrN coating on AISI H13 steel, but TZM alloy with TiAlN/CrN coating was found to be the best candidate as a mold for high temperature Cu semi-solid processing.

scholarly journals Boundary conditions for free surface inlet and outlet problems

2012 ◽  
Vol 708 ◽  
pp. 100-110 ◽  
Author(s):  
M. Taroni ◽  
C. J. W. Breward ◽  
P. D. Howell ◽  
J. M. Oliver
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Capillary Number ◽  
A Priori ◽  
Contact Angles ◽  
Local Behaviour ◽  
Coating Flows ◽  
Film Forming ◽  
Critical Capillary Number ◽  
Field Behaviour

AbstractWe investigate and compare the boundary conditions that are to be applied to free-surface problems involving inlet and outlets of Newtonian fluid, typically found in coating processes. The flux of fluid is a priori known at an inlet, but unknown at an outlet, where it is governed by the local behaviour near the film-forming meniscus. In the limit of vanishing capillary number $\mathit{Ca}$ it is well known that the flux scales with ${\mathit{Ca}}^{2/ 3} $, but this classical result is non-uniform as the contact angle approaches $\lrm{\pi} $. By examining this limit we find a solution that is uniformly valid for all contact angles. Furthermore, by considering the far-field behaviour of the free surface we show that there exists a critical capillary number above which the problem at an inlet becomes over-determined. The implications of this result for the modelling of coating flows are discussed.

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