OPERATING CAPACITY OF ANTI-OXIDIZING COATING IN HYPERSONIC FLOWS OF AIR PLASMA

2019 ◽  
Vol 26 (02) ◽  
pp. 1850145 ◽  
Author(s):  
ALEXEY N. ASTAPOV ◽  
EKATERINA L. KUZNETSOVA ◽  
LEV N. RABINSKIY
Keyword(s):  
Oxide Film ◽  
Ceramic Composites ◽  
Hypersonic Flows ◽  
Protective Film ◽  
Air Plasma ◽  
Main Layer ◽  
Operating Capacity ◽  
Heat Resistant ◽  
Wide Range ◽  
Erosion Loss

In this paper, we present the results of investigations of degradation processes that occur in the structure promising high-temperature anti-oxidizing of heat-resistant coating of the Si–TiSi2–MoSi2–B–Y system in hypersonic flows of air plasma. The coating is designed to protect a wide range of heat-resistant materials (carbon–carbon and carbon–ceramic composites, coal–graphite materials, alloys based on Nb, Mo, W, etc.). It is found that the coating operating capacity at surface temperatures [Formula: see text] 1820–1830∘C is provided by the structural-phase state of its microcomposite main layer and formation on the coating surface of a heterogeneous passivating protective film. It is based on borosilicate glass reinforced by rutile microneedles. The mechanism of coating destruction at [Formula: see text] 1850–1860∘C is erosion loss of oxide film as well as generation and growth of gas-filled cavities at the “coating main layer–oxide film” interface. As the pressure of saturated vapor of gaseous oxidation products (SiO, CO, MoO3 and B2O3) exceeds that of the ambient, the oxide film integrity is disrupted and oxidation process becomes active. The rates of erosion loss and sublimation grow as operating temperature increases and ambient pressure decreases.

Investigation of Destruction Mechanisms for Heat-Resistant Coatings in Hypersonic Flows of Air Plasma

2017 ◽  
Vol 269 ◽  
pp. 14-30 ◽  
Author(s):  
Alexey N. Astapov ◽  
Lev N. Rabinskiy
Keyword(s):  
Oxide Film ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Hypersonic Flows ◽  
Oxidation Products ◽  
Protective Film ◽  
Air Plasma ◽  
Main Layer ◽  
Heat Resistant ◽  
Erosion Loss

The authors present the results of investigations of degradation processes that occur in the structure of heat-resistant coating of the Si-TiSi2-MoSi2-B-Y system in hypersonic flows of air plasma. It is found that coating operating capacity at surface temperatures Tw ≤ 1820÷1830°C is provided by the structural-phase state of its microcomposite main layer and formation on the coating surface of a heterogeneous passivating protective film. It is based on borosilicate glass reinforced by rutile microneedles. The mechanism of coating destruction at Tw ≥ 1850÷1860°C is erosion loss of oxide film as well as generation and growth of gas-filled cavities at the "coating main layer–oxide film" interface. As the pressure of saturated vapor of gaseous oxidation products (SiO, CO, MoO3 and B2O3) exceeds that of the ambient, the oxide film integrity is disrupted and oxidation process becomes active. The rates of erosion loss and sublimation grow as operating temperature increases and ambient pressure decreases.

scholarly journals Oxidation Resistance of a Si–TiSi2–MoSi2–TiB2–CaSi2 Coating on a Cf/C–SiC Substrate in High-Speed High-Enthalpy Air Plasma Flows

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2637
Author(s):  
Alexey Astapov ◽  
Lev Rabinskiy ◽  
Olga Tushavina
Keyword(s):  
Oxide Film ◽  
Oxidation Resistance ◽  
High Speed ◽  
Protective Action ◽  
Structural Phase ◽  
Silicon Monoxide ◽  
Air Plasma ◽  
Plasma Flows ◽  
Main Layer ◽  
Static Conditions

The results of a study on the development and testing of a heat-resistant coating in a Si–TiSi2–MoSi2–TiB2–CaSi2 system to protect Cf/C–SiC composites from oxidation and erosional entrainment in high-speed flows are presented here. The coating was formed using firing fusion technology on the powder composition. Oxidation resistance tests were carried out under static conditions in air at 1650 °C and under conditions of interaction with high-speed air plasma flows, with Mach numbers M = 5.5–6.0 and enthalpy 40–50 MJ/kg. The effectiveness of the protective action of the coating was confirmed at surface temperatures of Tw = 1810–1820 °C for at least 920–930 s, at Tw = 1850–1860 °C for not less than 510–520 s, at Tw = 1900–1920 °C for not less than 280–290 s, and at Tw = 1940–1960 °C for not less than 100–110 s. The values of the rate of loss of the coating mass and the rate constant of heterogeneous recombination of atoms and ions of air plasma on its surface were estimated. The performance of the coating was ensured by the structural-phase state of its main layer, and the formation and evolution on its surface during operation of a passivating heterogeneous oxide film. This film, in turn, is composed of borosilicate glass with titanium and calcium liquation inhomogeneities, reinforcing TiO2 microneedles and in situ Si2ON2 fibers. It was shown that at Tw≥ 1850–1860 °C, the generation of volatile silicon monoxide was observed at the “oxide layer–coating” interface, followed by the effects of boiling and breakdown degradation of the oxide film, which significantly reduced the lifespan of the protective action of the coating.

Calculation of plasma centrifugal spraying parameters of fine granules of heat-resistant nickel alloys

2020 ◽  
pp. 471-474
Author(s):  
M.G. Yagodin ◽  
E.I. Starovoytenko
Keyword(s):  
Powder Metallurgy ◽  
Nickel Alloys ◽  
Dynamic Pressure ◽  
Calculated Data ◽  
Powder Size ◽  
Metal Powders ◽  
Heat Resistant ◽  
Gas Dynamic ◽  
Spraying Parameters ◽  
Wide Range

The equipment for the production of wide range of metal powders purposed for powder metallurgy is described. The possibility for producing of powders by the plasma centrifugal spraying is considered taking into account the gas dynamic pressure. The calculated data on the powder size for different materials are given.

scholarly journals Nano-Crystallization of Ln-Fluoride Crystals in Glass-Ceramics via Inducing of Yb3+ for Efficient Near-Infrared Upconversion Luminescence of Tm3+

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1033
Author(s):  
Jianfeng Li ◽  
Yi Long ◽  
Qichao Zhao ◽  
Shupei Zheng ◽  
Zaijin Fang ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Glass Ceramics ◽  
Upconversion Emission ◽  
Ceramic Composites ◽  
Wide Range ◽  
Transmission Window ◽  
Optical Applications ◽  
Upconversion Emissions

Transparent glass-ceramic composites embedded with Ln-fluoride nanocrystals are prepared in this work to enhance the upconversion luminescence of Tm3+. The crystalline phases, microstructures, and photoluminescence properties of samples are carefully investigated. KYb3F10 nanocrystals are proved to controllably precipitate in the glass-ceramics via the inducing of Yb3+ when the doping concentration varies from 0.5 to 1.5 mol%. Pure near-infrared upconversion emissions are observed and the emission intensities are enhanced in the glass-ceramics as compared to in the precursor glass due to the incorporation of Tm3+ into the KYb3F10 crystal structures via substitutions for Yb3+. Furthermore, KYb2F7 crystals are also nano-crystallized in the glass-ceramics when the Yb3+ concentration exceeds 2.0 mol%. The upconversion emission intensity of Tm3+ is further enhanced by seven times as Tm3+ enters the lattice sites of pure KYb2F7 nanocrystals. The designed glass ceramics provide efficient gain materials for optical applications in the biological transmission window. Moreover, the controllable nano-crystallization strategy induced by Yb3+ opens a new way for engineering a wide range of functional nanomaterials with effective incorporation of Ln3+ ions into fluoride crystal structures.

scholarly journals The high temperature oxidation of metals

1926 ◽  
Vol 111 (757) ◽  
pp. 203-209 ◽  
Keyword(s):  
High Temperature ◽  
Oxide Film ◽  
High Temperature Oxidation ◽  
Protective Action ◽  
Protective Film ◽  
Parent Metal ◽  
Compact Structure ◽  
Temperature Oxidation ◽  
Protective Properties ◽  
Porous Oxide

The oxidation of metals at high temperatures has been investigated with some thoroughness by Pilling and Bedworth. They found that the metals could be divided into two great classes according to the nature of the oxide produced. If the volume of the oxide is greater than that of the metal from which it was produced an oxide film of compact structure and protective properties will be produced. If the volume of the oxide is less than that of its parent metal a porous oxide is produced which has no protective action whatever. The oxidation of the metals of the first class is controlled by the diffusion of oxygen through the protective film of oxide and the application of the diffusion laws to this process lead us to expect that the oxidation law will be W 2 = K t W 2 = amount of oxygen absorbed t = time K is a constant.

Multi-Purpose Porous Ceramic Material

2018 ◽  
Vol 931 ◽  
pp. 594-597
Author(s):  
Yu.S. Bagaiskov
Keyword(s):  
Ceramic Material ◽  
Construction Material ◽  
Porous Ceramic ◽  
Ceramic Composites ◽  
Refractory Clay ◽  
Treatment Processes ◽  
Wide Range ◽  
Porosity And Permeability ◽  
And Performance ◽  
Criteria For Evaluation

The main criteria for evaluation of ceramic products’ properties are strength, structural and mechanical, and thermophysical properties. To produce ceramic composites with a wide range of structural, mechanical, strength, and performance properties depending on application, various additives (flux agents, sintering agents, fillers) and heat treatment processes are used. Studies to determine a rational mixture composition have been carried out. A multipurpose material, comprising particles of the basic chamotte filler (burned clay) with a bonding agent in the form of refractory clay from the Latnenskoye deposit with a field spar fluxing agent, an additional filler made of heat-resistant silicon carbide, and an adhesive component in the form of powdered dextrin, is suggested. According to the combination of its ensured parameters, the obtained ceramic material can be multipurpose. Its degree of porosity and permeability make the material filtering, sound-proofing, and heat-retaining; considering the low density, it can be used as a lightweight construction material.

High-Temperature Oxidation Behaviors of 30Cr25Ni20Si Heat-Resistant Steel in Air

2020 ◽  
Vol 861 ◽  
pp. 83-88
Author(s):  
You Yang ◽  
Xiao Dong Wang
Keyword(s):  
High Temperature ◽  
Oxide Film ◽  
High Temperature Oxidation ◽  
Film Growth ◽  
Surface Oxidation ◽  
Mass Gain ◽  
Resistant Steel ◽  
Temperature Oxidation ◽  
Heat Resistant Steel ◽  
Heat Resistant

High temperature oxidation dynamic behaviors and mechanisms for 30Cr25Ni20Si heat-resistant steel were investigated at 800, 900 and 1000°C. The oxide layers were characterized by scanning electron microscopy (SEM-EDS), X-ray diffractometer (XRD). The results showed that the oxidation rate of test alloys is increased with increasing the oxidation time. The oxidation dynamic curves at 800 and 900°C follow from liner to parabolic oxidation law. The transition point is 10 h. At 1000°C, the steel exhibits a catastrophic oxidation, and the oxidation mass gain value at 50 h is 0.77 mg/cm2. This suggests that the steel at 900°C has formed a dense protective surface oxidation film, effectively preventing the diffusion of the oxygen atoms and other corrosive gas into the alloy. Therefore, at the first stage of oxidation, chemical adsorption and reaction determine the oxide film composition and formation process. At the oxide film growth stage, oxidation is controlled by migration of ions or electrons across the oxide film. When the spinel scale forms, it acts as a compact barrier for O element and improving the oxidation resistance.

Thermodynamic and Transport Properties of Real Air Plasma in Wide Range of Temperature and Pressure

2016 ◽  
Vol 18 (7) ◽  
pp. 732-739 ◽  
Author(s):  
Chunlin Wang ◽  
Yi Wu ◽  
Zhexin Chen ◽  
Fei Yang ◽  
Ying Feng ◽  
...  
Keyword(s):  
Transport Properties ◽  
Air Plasma ◽  
Wide Range ◽  
Thermodynamic And Transport Properties ◽  
Temperature And Pressure

scholarly journals Heat resistant polymer electrolyte for enhanced organic electrochromic windows based on poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)

2014 ◽  
Vol 1695 ◽  
Author(s):  
Nishita Anandan ◽  
Sooyeun Kim ◽  
Minoru Taya
Keyword(s):  
Counter Electrode ◽  
Elevated Temperatures ◽  
Test Chamber ◽  
Electrochemical Stability ◽  
Impedance Method ◽  
Optical Contrast ◽  
Heat Resistant ◽  
Working Electrode ◽  
Wide Range ◽  
Electrochromic Windows

ABSTRACTElectrochromic Windows(ECWs) have the potential to save energy through dynamic control of light and solar energy entering a room (via solar heat gain coefficient control). ECWs have been developed as an optical shutter in airplane, building and automobile applications. An ECW is composed of three components, a working electrode based on electrochromic materials, a counter electrode based on ion storage materials and the electrolyte as an ionic conducting layer. Organic ECWs have been gaining popularity due to easy and cost effective manufacturing, availability of wide range of colors, high optical contrast and flexibility in design. However there are challenges in commercialization and application of organic ECWs. The application of ECWs as a sunroof in automobiles demands operation in harsh environment conditions like elevated temperature. Consequently the University of Washington, Center for Intelligent Materials and Systems has been developing a heat resistant organic ECW that can be operated at elevated temperatures maintaining high optical contrast, fast switching speed, optical color memory and electrochemical stability. The proposed design is an ECW based on poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine),PPRODOT-Me2 as a working electrode, V2O5-TiO2 composite materials as a counter electrode and poly(ethylene imine) based electrolyte. The ionic conductivity of the electrolyte was calculated through complex impedance method and temperature dependence of the electrolyte was determined using environment test chamber to control a temperature range of 15 to 80o Celsius for 100 hours. A 76 × 76 mm2 ECW was developed and the optical transmittance change was observed by Chronoamperomerty and Time course measurement. The electrochemical stability of the window was monitored using cyclic voltammetry. The developed electrochromic window showed good optical contrast, electrochemical stability and fast response time after testing at elevated temperatures for 100 hours.

scholarly journals Properties of glasses in the system BaO–B2O3–SiO2–xAl2O3 (x=0; 5; 10 mol.%)

2021 ◽  
pp. 83-89
Author(s):  
Yu.S. Hordieiev ◽  
◽  
E.V. Karasik ◽  
А.A. Amelina ◽  
◽  
...  
Keyword(s):  
Chemical Composition ◽  
Glass Ceramic ◽  
Glass Formation ◽  
Linear Thermal Expansion ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Heat Resistant ◽  
Glass Ceramic Materials ◽  
Wide Range ◽  
Physical And Chemical

This article shows the prospect of the system BaO–Al2O3–B2O3–SiO2 as the basis of vitreous and glass ceramic materials, which are widely used in rocket production for high-temperature protection of heat resistant alloys, in the power industry for sealing solid oxide fuel cells, and in the production of heat resistant glass ceramic materials. We examined the conditions of glass formation and properties of glasses with the following content of components (mol.%): BaO 30–70, B2O3 10–50, SiO2 20–60, and Al2O3 0–10. We established experimentally that the physical and chemical properties of glass, depending on its chemical composition, vary within the following limits: coefficient of linear thermal expansion of (71–122)10–7 К–1; glass transition temperature of 500–6500С; dilatometric softening point of 540–6700С; and density of 3.20–4.21 g cm–3. The volume resistivity of the studied glasses is within 1011–1013 Ohmcm at the temperature of 1500С. Generalization of the dependences of glass properties on their chemical composition was carried out with the use of the additive equations, for which the partial contributions of oxides to the values of the corresponding properties were determined by experimental and statistical methods. The established patterns of influence of components and conditions of glass formation on the physical and chemical characteristics of glasses allows implementing the process of designing of a wide range of glass compositions with the complex of specified properties in order to solve the tasks of their practical use.

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