scholarly journals Study of the thermal stability of foam of different expansion ratio

2020 ◽  
Vol 29 (3) ◽  
pp. 103-110
Author(s):  
A. V. Koksharov ◽  
S. I. Osipenko ◽  
E. V. Gaynullina
Keyword(s):  
Thermal Stability ◽  
Thermal Exposure ◽  
Expansion Ratio ◽  
Heat Fluxes ◽  
Foam Layer ◽  
Destructive Effect ◽  
Foam Expansion ◽  
Destruction Rate ◽  
Wide Range ◽  
Thermal Stability Of

Introduction. Currently, the industry produces a wide range of foam generators to produce fire-extinguishing foams, and the foams they produce differ significantly in their expansion ratio and, consequently, fire resistance. Since heat fluxes have the main destructive effect on the foam, the purpose of this paper is to establish the patterns of destruction of foam of different expansion ratio when heated.Methods of research. The foam with expansion ratio from 7.5 to 80 was used for the tests. It was obtained by mechanical beating of 6 % solution of foaming agent PO-6RZ. The thermal stability of the foam was studied when the heat flow from the gas burner flame affects the foam layer. During the experiment, the change in the height of the foam column in time was recorded.Results and Discussion. The results of measurements, presented in the form of dependence of foam layer destruction rate on time, quantity of released liquid phase on 1 m2·s, dependence of foam layer destruction rate on its density allowed revealing a number of patterns. The destruction rate of foam with an expansion ratio of up to 30 remains constant throughout the entire duration of thermal exposure. As the foam expansion ratio increases, the rate of destruction at the initial stage of heat flux exposure increases. With a foam expansion ratio of more than 50, there is initially a sharp increase in the rate of destruction, which subsequently decreases as the foam column decreases. In the conditions of the experiment, the best characteristics were shown by the foam with an expansion ratio of 50, because in the foam with a smaller expansion ratio the syneresis makes a significant contribution to its destruction, and the foams with a larger expansion ratio are destroyed by the mechanical effect of convective flame flows.Conclusion. The study of the foam destruction patterns under thermal impact allowed establishing the fact that its destruction is limited by the rate of impoverishment of the upper layers with liquid.

Thermal Decomposition of Supersaturated Ti1-xAlxN Solid Solution Synthesized by High-Energy Milling

2016 ◽  
Vol 9 ◽  
pp. 82-89
Author(s):  
Maya Radune ◽  
Michael Zinigrad ◽  
David Fuks ◽  
S. Hayun ◽  
Nachum Frage
Keyword(s):  
Thermal Stability ◽  
Solid Solution ◽  
Spinodal Decomposition ◽  
Density Functional ◽  
Chemical Deposition ◽  
High Energy ◽  
Nucleation And Growth ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Thermal Stability Of

Supersaturated titanium-aluminum nitride (Ti1-xAlxN) is a very attractive material for a wide range of applications due to its high oxidation and wear resistance accompanied by high strength, hardness, thermal conductivity and thermal shock resistance. Currently, its applications are limited to coatings obtained by physical or chemical deposition. Bulk materials based on Ti1-xAlxN may be fabricated by powder metallurgy approach using powders synthesized by high-energy ball milling (HEBM), which composition corresponds to supersaturated Ti1-xAlxN solid solution. In the present study, thermal stability of the supersaturated Ti1-xAlxN solid solution was investigated. According to the quasi-binary TiN-AlN phase diagram, constructed using density functional theory (DFT) analysis, the concentration ranges, where decomposition takes place through spinodal decomposition or through nucleation and growth, were determined. Experimental study on thermal stability of solid Ti1-xAlxN solution powder was conducted by means of differential scanning calorimetry (DSC), Brunauer-Emmited-Teller (BET) and XRD. The results indicated that spinodal decomposition of Ti1-xAlxN starts at 800°C, while at temperature higher than 1300°C regular decomposition (nucleation and growth) is occur.

Thermal stability of nanocrystalline WC–Co powder synthesized by using mechanical milling at low temperature

2001 ◽  
Vol 16 (2) ◽  
pp. 478-488 ◽  
Author(s):  
Jianhong He ◽  
Leoanardo Ajdelsztajn ◽  
Enrique J. Lavernia
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Mechanical Milling ◽  
Gradual Increase ◽  
Thermal Exposure ◽  
X Ray Diffraction ◽  
Cryomilled Powder ◽  
X Ray ◽  
Increasing Temperature ◽  
Thermal Stability Of

Nanostructured WC–18% Co powder was synthesized by using cryogenic mechanical milling, and the thermal stability of the nanostructured powder was investigated in detail. The results indicated that the as-synthesized WC–18% Co powder had an average WC particle size of 25 nm. Growth of WC particles occurred above 873 K; however, the average WC particle size remained smaller than 100 nm in the powder isothermally heated for 4 h at 1273 K. Thermal exposure in air at T < 623 K did not result in significant oxidation of the cryomilled powder. The thermal exposure did promote the formation of WO2 and WO3 oxides. The Co6W6C phase was detected by x-ray diffraction in the powder heated in nitrogen at 1273 K, and the phases associated with decarburization of WC, such as W2C, W3C phases, were not observed. With increasing temperature, the dissolution of W and C elements in the Co matrix led to a gradual increase in {111} crystallographic plane spacing, eventually leading to the formation of an amorphous phase.

scholarly journals Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

2019 ◽  
Vol 15 ◽  
pp. 2311-2318 ◽  
Author(s):  
Andreas Boelke ◽  
Yulia A Vlasenko ◽  
Mekhman S Yusubov ◽  
Boris J Nachtsheim ◽  
Pavel S Postnikov
Keyword(s):  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Thermogravimetric Analysis ◽  
Systematic Investigation ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
C Decomposition ◽  
Thermal Stability Of ◽  
Peak Decomposition

The thermal stability of pseudocyclic and cyclic N-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-λ3-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. Peak decomposition temperatures (T peak) were observed within a wide range between 120 and 270 °C. Decomposition enthalpies (ΔH dec) varied from −29.81 to 141.13 kJ/mol. A direct comparison between pseudocyclic and cyclic NHIs revealed high T peak but also higher ΔH dec values for the latter ones. NHIs bearing N-heterocycles with a high N/C-ratio such as triazoles show among the lowest T peak and the highest ΔH dec values. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation.

Thermal Stability of NiAl-Base Coatings for High Temperature Application

2005 ◽  
Vol 237-240 ◽  
pp. 709-714
Author(s):  
Robert Filipek ◽  
Marek Danielewski ◽  
E. Tyliszczak ◽  
M. Pawełkiewicz ◽  
S. Datta
Keyword(s):  
Thermal Stability ◽  
Gas Turbines ◽  
Inverse Method ◽  
Critical Role ◽  
Diffusion Coatings ◽  
Aluminide Coatings ◽  
Wide Range ◽  
Industrial Energy ◽  
Temperature Application ◽  
Thermal Stability Of

Aluminide diffusion coatings act as a remedy against the aggressive environments in which modern aero-gas turbines operate. Platinum addition to basic aluminide coatings significantly improves the oxidation resistance of these coatings. The increase in operating temperatures of industrial energy systems and gas turbines, has led to the extensive use of coatings capable of providing improved service life. Interdiffusion plays a critical role in understanding the integrity of such coatings. The Danielewski-Holly model of interdiffusion which allows for the description of a wide range of processes (including processes stimulated by reactions at interfaces) is employed for studying of interdiffusion in the Pt-modified β-NiAl coatings. Using the inverse method the intrinsic diffusivities of Ni, Al and Pt were calculated. Such obtained diffusivities were subsequently used for modelling of thermal stability of Pt-modified aluminide coatings in air and in argon atmosphere.

Conductivity and Thermal-Stability of 5-Sulfosalicylic Acid Sodium Doped Polypyrrole

2010 ◽  
Vol 428-429 ◽  
pp. 579-582 ◽  
Author(s):  
Fu Fang Zhou ◽  
Bao Gai Zhai ◽  
Chun Xu Pan ◽  
Yuan Ming Huang
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Laser Light ◽  
Dopant Concentration ◽  
Laser Light Scattering ◽  
Probe Laser ◽  
Sulfosalicylic Acid ◽  
Wide Range ◽  
Thermal Stability Of

By varying the dopant-to-pyrrole ratio in a wide range from 0 to 60% a series of 5-sulfosalicylic acid sodium doped polypyrrole was synthesized in situ in aqueous solution with ferric chloride as the oxidant. The resulting polypyrroles were characterized with the four-probe, laser light scattering and thermo-gravimetry analysis, differential thermal analysis, respectively. Our results indicate that the particle size plays a determinative role to tune the conductivity in the studied range of dopant concentration; and this series of polypyrrole with size-tuned-conductivity exhibits little less thermal-stability although its size and conductivity changes simultaneously and acutely with the dopant concentration. The association of the conductivity with particle size was interpreted in terms of a theoretical model proposed by Baughman and Shacklelette.

scholarly journals Microstructure, Mechanical Properties, and Thermal Stability of Carbon-Free High Speed Tool Steel Strengthened by Intermetallics Compared to Vanadis 60 Steel Strengthened by Carbides

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1901
Author(s):  
Alena Michalcová ◽  
Vojtěch Pečinka ◽  
Zdeněk Kačenka ◽  
Jan Šerák ◽  
Jiří Kubásek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Tool Steel ◽  
High Speed ◽  
Intermetallic Phase ◽  
High Hardness ◽  
Thermal Exposure ◽  
Machining Process ◽  
Material Utilization ◽  
Thermal Stability Of

High speed tool steels are materials that exhibit superior mechanical properties (e.g., high hardness). They should also be resistant to thermal exposure to maintain high hardness during the machining process. In this paper, a C-free tool steel formed of Fe matrix and a Mo6Co7 intermetallic phase was studied. This steel was compared to the well-known Vanadis 60 steel containing Fe matrix and carbides. Microstructures were investigated by scanning (SEM) and transmission (TEM) electron microscopy, and the mechanical properties and thermal stability of both materials were compared. It was proven that the strengthening in the Vanadis 60 steel was mainly caused by the carbides, while the C-free steel was strengthened by the Mo6Co7 phase. The hardness values of both materials were comparable in the utilization state (approx. 950 HV). The hardness of Vanadis 60 steel decreased after several minutes of annealing at 650 °C under the value that enables material utilization. The hardness value of the steel strengthened by the intermetallics also decreased but significantly slower. Based on these results, the main finding of this study is that the C-free steel exhibited much better thermal stability and may be utilized at higher temperatures for longer periods of time than Vanadis 60.

MECHANICAL PROPERTIES OF BAMBOO POWDER REINFORCED ETHYLENE PROPYLENE DIENE MONOMER (EPDM) COMPOSITES: EFFECT OF FILLER LOADING AND PARTICLE SIZE

2014 ◽  
Vol 6 (2) ◽  
pp. 1122-1134 ◽  
Author(s):  
Mokhtar Hemdan Abd El-Salam
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Particle Size ◽  
Internal Friction ◽  
Thermo Gravimetric Analysis ◽  
Filler Loading ◽  
Gravimetric Analysis ◽  
Wide Range ◽  
Bamboo Powder ◽  
Thermal Stability Of

Due to the light weight, high specific strength and non hazardous nature of bamboo fiber, it is preferred over synthetic fibers in composite materials for a wide range of applications such as automotive industry and including household sectors. As was noticed, little attention has been given to the effect of bamboo powder on the mechanical properties of rubber composites. Hence, an attempt has been made in this paper to the study the effect of loading and particle size of bamboo powder on the mechanical properties of EPDM composites. Thermo-gravimetric analysis (TGA) was carried out to study the thermal stability of composites. Results indicated that the thermal stability of EPDM was further improved with increasing in bamboo loading and decreasing in particle size. The stress- strain curves of the composites were studied and fitted according toOgden’s model. Mechanical parameters for the studied composites were improved with increasing bamboo loading. Besides, properties such as rupture stress, and internal friction were found to be maximum for composites containing certain content of bamboo powder, depending upon its particle size. Moreover, composites containing the smallest particle size of powder, at all levels of bamboo loading, showed mechanical properties superior to all other composites. From the dynamic mechanical measurements, the dynamic modulus, internal friction, and thermal diffusivity were calculated. The observed variations were explained in view of the role played by both the loading level and the particle size of bamboo powder. These findings were supported by scanning electron microscopy (SEM) micrographs.

THERMAL GRAVIMETRIC AND ACTIVATION ENERGY ANALYSIS OF RENEWABLE POLYMER UPON ULTRAVIOLET (UV) IRRADIATION

2015 ◽  
Vol 77 (32) ◽  
Author(s):  
Nik Normunira Mat Hassan ◽  
Anika Zafiah M. Rus
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Uv Irradiation ◽  
Hard Segment ◽  
Soft Segment ◽  
Great Influence ◽  
Automotive Application ◽  
Polymer Foam ◽  
Wide Range ◽  
Thermal Stability Of

Renewable polymer made from renewable material is one of the most important groups of polymer because of their versatility and they can be manufactured in a wide range of insulation and automotive application. In this project, renewable polymer based on waste vegetable oil were synthesized and crosslink with commercial polymethane polyphenyl isocyanate. The renewable polymer foam (RPF) was compressed by using hot compression moulding technique at 90 oC based on the evaporation of volatile matter and known as compressed renewable polymer (CRP). The thermal degradation and activation energy of RPF and CRP samples is consistant with the increasing of UV irradiation time at the first degradation, second degradation and third degradation. This is due to thermal stability of samples at the hard segment has a great influence on the thermal stability of soft segment. A higher thermal stability of hard segment leads to a higher degradation temperature of soft segment.

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