scholarly journals Estimation of anti-icing properties of coatings

2019 ◽  
Vol 135 ◽  
pp. 01009
Author(s):  
Valentina Loganina ◽  
Svetlana Kislitsyna
Keyword(s):  
Initial Period ◽  
Wetting Angle ◽  
Silicone Resin ◽  
Thermal Imager ◽  
Freezing Front ◽  
Properties Of Coatings ◽  
Metal Structures ◽  
Wetting Hysteresis ◽  
Inclined Surface ◽  
Kinetics Of

The proposed composition for anti-icing coating of metal structures. The composition contains as the filler used aerosil brand R 972 with a density of 2360 kg / m3, particle size of 16 nm and a specific surface 12000 m2 / kg. Silicone resin SILRES® MSE 100 with a 10% concentration was used as a binder. The degree of hydrophobicity was estimated by the value of the wetting angle. In order to characterize the anti-icing properties of the coatings, we used the static and dynamic (advancing and retreating) wetting angle, as well as wetting hysteresis, for which we measured the angles of leakage, and the angles of drift from. Studies of the dynamics of freezing drops on the surface were performed using a TESTO 875-1 thermal imager. It is shown, that the hysteresis of wetting of the superhydrophobic surface based on the developed composition is 3.7 degrees. The critical angle of rolling drops of water from an inclined surface is determined. In the study of the kinetics of freezing of a drop of water on a metal surface, an uneven distribution of temperature on the surface of a drop of water is observed. The process of freezing drops is multistage. In the initial period, there is a transfer of heat from the surface to a drop of water. This stage is followed by the process of freezing the drop, which is manifested in the movement of the freezing front from the substrate upwards.

Development of Superhydrophobic Coatings for Metal Surfaces

2020 ◽  
Vol 839 ◽  
pp. 14-19
Author(s):  
Valentina I. Loganina
Keyword(s):  
Water Droplet ◽  
Superhydrophobic Surface ◽  
Metal Surfaces ◽  
Critical Angle ◽  
Initial Period ◽  
Freezing Front ◽  
Properties Of Coatings ◽  
Superhydrophobic Coatings ◽  
Inclined Surface ◽  
Kinetics Of

Provides information about the results of the evaluation of anti-icing properties of coatings. It is shown, that the hysteresis of wetting of the superhydrophobic surface based on the developed composition is 3,7 degrees. The critical angle of rolling of a drop of water from an inclined surface is determined. The results of the evaluation of the kinetics of freezing of a water droplet on a superhydrophobic surface are given. It is shown, that in the initial period there is a transfer of heat from the surface to a drop of water. Then there is a movement of the freezing front from the substrate upwards.

scholarly journals Research of freezing kinetics of water drop on superhydrophobic coating surfaces

Vestnik MGSU ◽  
2019 ◽  
pp. 435-441
Author(s):  
About the author: Valentina I. Loganina
Keyword(s):  
Temperature Distribution ◽  
Superhydrophobic Surface ◽  
Water Drop ◽  
Initial Period ◽  
Technical Problem ◽  
Superhydrophobic Surfaces ◽  
Silicone Resin ◽  
Thermal Imager ◽  
Upward Movement ◽  
Kinetics Of

Introduction. Anti-icing coatings are used to prevent icing of the building roofs and power transmission line poles. One of the characteristics of anti-icing properties of superhydrophobic surfaces is the delay in the crystallization of drops on such surfaces. A significant delay in the crystallization of water drops on superhydrophobic substrates is noted in the scientific and technical literature. However, it is recorded in a number of papers that the delay time of crystallization on hydrophilic substrates is longer than the corresponding values on superhydrophobic surfaces. In connection with the foregoing, the study of the freezing kinetics of a water drop on a superhydrophobic surface in order to assess its efficiency is a relevant scientific and technical problem. Materials and methods. To evaluate the kinetics of freezing a of water drop on a superhydrophobic surface, the following experiment is conducted. A drop of water is placed on the superhydrophobic surface of the mortar substrate, which is placed in a freezer at a temperature of –18 °C. Studies of the drop freezing dynamics on the surface are performed using a Testo 875-1 thermal imager. To create a superhydrophobic surface, an aerosil R 972 with density ρ = 2360 kg/m3, particle size of 16 nm and specific surface area Ssp = 12 000 m2/kg is used as a filler. A silicone resin SILRES® MSE 100 of 10 % concentration is used as a binder. The obtained solutions are deposited on the mortar substrates. The degree of hydrophobicity is assessed by the magnitude of the wetting angle (θ°). Results. Results of the studies of temperature distribution on the water drop surface indicate that the distribution is uneven. The process of drop freezing is multistage. In the initial period, there is a transfer of heat from the surface into the water drop. This stage is followed by the process of drop freezing which is manifested in the upward movement of the freezing front from the substrate. Conclusions. It is revealed that the temperature distribution on the surface of a water drop is uneven. When freezing, a water drop has a pointed top.

The mechanism of the anionic coordination polymerization of isoprene

1980 ◽  
Vol 45 (9) ◽  
pp. 2391-2399 ◽  
Author(s):  
Miroslav Kašpar ◽  
Jiří Trekoval
Keyword(s):  
Chromatographic Method ◽  
Initial Period ◽  
Reaction Scheme ◽  
Polymerization Kinetics ◽  
Coordination Polymerization ◽  
Initial Concentration ◽  
The Cross ◽  
Gas Chromatographic Method ◽  
Kinetics Of

The polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene with butyllithium as the initiator was investigated by the gas chromatographic method. After completion of the initial period of the reaction, its order with respect to the initial concentration of initiator is negative at the concentrations of the latter between 0.01 and 0.25 mol/l, and positive at higher concentrations. A reaction scheme has been suggested with respect to the "cross" association of butyllithium and of the "living" oligoisoprene.

Vulcanization of Rubber in the Presence of N,N-Diethyl-2-Benzothiazolylsulfenamide as Accelerator

1960 ◽  
Vol 33 (2) ◽  
pp. 361-372 ◽  
Author(s):  
B. A. Dogadkin ◽  
O. N. Beliatskaya ◽  
A. B. Dobromyslova ◽  
M. S. Feldshtein
Keyword(s):  
Induction Period ◽  
Maximum Rate ◽  
Initial Period ◽  
Pure Oxygen ◽  
Butadiene Rubber ◽  
Sulfur Vulcanization ◽  
Analogous Manner ◽  
Chemical Crosslinks ◽  
Main Period ◽  
Kinetics Of

Abstract 1. The vulcanization of rubber in the presence of N,N-diethyl-2-benzothiazolylsulfenamide is characterized by an S-shaped curve for the addition of sulfur with an initial induction period in the reaction. The modulus and number of crosslinks are changed in an analogous manner to the structure of the vulcanizate. 2. The energy of activation of the addition of sulfur in the initial period is equal to 30 kcal per mole as against 14 kcal per mole in the main period. 3. The induction period is increased if the sodium-butadiene rubber is purified from alkali. 4. Molecular oxygen present in the compound being vulcanized decreases the induction period and increases the rate of the addition of the sulfur in the main period. An induction period is not observed when vulcanization is carried out in an atmosphere of pure oxygen. 5. The interaction of N,N-diethyl-2-benzothiazolylsulfenamide with rubber (in the absence of sulfur) at vulcanization temperatures is accompanied by the formation of MBT, diethylamine, and the addition of the elements of the accelerator to the rubber. The kinetics of this process were studied. 6. The interaction of N,N-diethyl-2-benzothiazolyl sulfenamide with rubber leads to the formation of chemical crosslinks between the molecules of rubber (the effect of vulcanization). 7. The change of N,N-diethyl-2-benzothiazolyl sulfenamide under the conditions of normal sulfur vulcanization has the same character as in the interaction of it with rubber. The kinetics of the formation of MBT have a maximum which coincides with the maximum rate of the addition of sulfur to the rubber. 8. A mechanism is presented for the vulcanization and acceleration actions of N,N-diethyl-2-benzothiazolyl sulfenamide which provides for the extraction of hydrogen by the accelerator radicals from the molecular chains of the rubber with the formation of MBT, diethylamine and polymer radicals which are able to interact with the sulfur.

scholarly journals Effects of freezing on soil temperature, freezing front propagation and moisture redistribution in peat: laboratory investigations

2012 ◽  
Vol 16 (2) ◽  
pp. 501-515 ◽  
Author(s):  
R. M. Nagare ◽  
R. A. Schincariol ◽  
W. L. Quinton ◽  
M. Hayashi
Keyword(s):  
Water Content ◽  
Active Layer ◽  
Water Movement ◽  
Peat Soil ◽  
Soil Column ◽  
Initial Period ◽  
Soil Freezing ◽  
Permafrost Soil ◽  
Freezing Front ◽  
Discontinuous Permafrost

Abstract. There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost). Soil water movement towards the freezing front (from warmer to colder regions) was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice) propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.

scholarly journals Kinetics of structure formation of a composite mortar with nano-additives based on aluminium

2020 ◽  
Vol 161 ◽  
pp. 01099
Author(s):  
S.Yu. Efremova ◽  
M.I. Panfilova ◽  
N.I. Zubrev ◽  
O.V. Novoselova
Keyword(s):  
Structure Formation ◽  
Temporal Evolution ◽  
Initial Period ◽  
Control Sample ◽  
Injection Efficiency ◽  
Evolution Of Structure ◽  
Nano Additives ◽  
Kinetics Of

This paper discusses the possibility of using aluminum-containing nano-additives as structure modifiers of composite mortar in order to ensure safety and durability of rubble foundation. Higher injection efficiency can be achieved by integrating the composite mortar into the foundation body. The temporal evolution of structure formation in composite mortar with various contents of boehmite and aluminosilicate nanotubes (ANT) was studied. The optimal concentrations of additives were determined at which the rate of structure formation reaches its maximum. It was revealed that ANT additives accelerate the hardening time of the composite mortar by 1.3 times in comparison with boehmite additives. The greatest impact on accelerating the structure formation in the initial period is achieved by adding 0.125% aluminosilicate tubes to the mass of cement. It was found that in this case, the duration of flowability loss of the composite mortar is reduced by a factor of three compared with that of the control sample.

scholarly journals Modelling Water Absorption in Micronized Lentil Seeds with the Use of Peleg’s Equation

2019 ◽  
Vol 12 (1) ◽  
pp. 261
Author(s):  
Izabela Kuna-Broniowska ◽  
Agata Blicharz-Kania ◽  
Dariusz Andrejko ◽  
Agnieszka Kubik-Komar ◽  
Zbigniew Kobus ◽  
...  
Keyword(s):  
Sustainable Development ◽  
Water Absorption ◽  
Absorption Rate ◽  
Initial Period ◽  
Infrared Emission ◽  
Heating Time ◽  
Infrared Irradiation ◽  
Pre Treatment ◽  
Peleg’S Equation ◽  
Kinetics Of

The aim of the paper was to investigate the effect of infrared pre-treatment on the process of water absorption by lentil seeds. The paper presents the effects of micronization on the process of water absorption by lentil seeds. As a source of infrared emission, 400-W ceramic infrared radiators ECS-1 were used. The seeds were soaked at three temperature values (in the range from 25 to 75 °C) for 8 h, that is, until the equilibrium moisture content was achieved. Peleg’s equation was used to describe the kinetics of water absorption by lentil seeds. The results were compared with those obtained in the process of soaking crude seeds. On the basis of the conducted research, it was found that the infrared pre-treatment contributed to a substantial increase in the water absorption rate in the initial period of soaking lentil seeds (especially at 25 °C). Infrared irradiation can be an effective method for intensification of lentil seed hydration at an ambient temperature. It should be assumed that, in accordance with the principles of sustainable development, shortening the heating time will significantly reduce the energy consumption and cost of processing lentil seeds.

Glancing Angle X-Ray Study of Crystallization of Amorphous Ge at the Ge-A1 Interface

1990 ◽  
Vol 202 ◽  
Author(s):  
S. M. Heald ◽  
J. K. D. Jayanetti ◽  
R. C. Budhani
Keyword(s):  
Initial Period ◽  
Time Characteristic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffusion Limited ◽  
Glancing Angle ◽  
Lower Temperature ◽  
Kinetics Of ◽  
Diffusion Limited Reaction ◽  
Good Agreement

ABSTRACTThe amorphous to crystalline transformation of Ge in Al/Ge thin film couples has been studied using glancing angle EXAFS, x-ray reflectivity and diffraction. It was found that crystallization occurs at a much lower temperature (118-150 °C) than for bulk Ge, and initiates at the Al/Ge interface. X-ray diffraction studies were made at 152 °C to study the kinetics of the reaction. After an initial period we find good agreement with a square root dependence of the time, characteristic of a diffusion limited reaction.

Kinetics of ASAM and Kraft Pulping of Eucalypt Wood (Eucalyptus globulus)

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 85-90 ◽  
Author(s):  
Isabel Miranda ◽  
Helena Pereira
Keyword(s):  
Eucalyptus Globulus ◽  
Initial Period ◽  
Reaction Times ◽  
Kraft Pulping ◽  
Kraft Pulps ◽  
Final Phase ◽  
Lower Mass ◽  
Lignin Removal ◽  
Mass Losses ◽  
Kinetics Of

Summary The kinetics of ASAM and kraft pulping of eucalypt wood (Eucalyptus globulus) were studied in relation to delignification and polysaccharide removal. In comparison to kraft, ASAM pulping had lower mass losses and delignification for the same temperature and reaction times (59.2% at Kappa 25 vs 50.0% at Kappa 17, at 180°C). The ASAM pulps have a higher brightness. ASAM pulping had a short initial period with no mass loss and lignin removal, followed by two reaction phases: a main phase where 61% of lignin was removed (at 180°C) and a subsequent final phase. In comparison to kraft, the main delignification rates of ASAM pulping were approximately 2.5 slower (at 180°C, −1.8 × 10−2 min−1 for ASAM and −4.2 × 10−2 for kraft pulping), and the calculated Arrhenius activation energies were higher (132.4 kJ mol−1 and 83.5 kJ mol−1, respectively). The loss of cellulose was relatively small (12.5 %) and lower than in kraft pulps.

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