scholarly journals Crystallization Behavior of Phosphate Glasses with Hydrophobic Coating Materials

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Jaeyeop Chung ◽  
Bongki Ryu
Keyword(s):  
Crystallization Behavior ◽  
Glass Frit ◽  
Contact Angles ◽  
Exothermic Peak ◽  
Phosphate Glasses ◽  
Coating Materials ◽  
Hydrophobic Coating ◽  
Coated Surface ◽  
Diffraction Peaks ◽  
Strong Exothermic Peak

We analyzed the effect of the addition of Li2O3, TiO2, and Fe2O3on the crystallization behavior of P2O5–CaO–SiO2–K2O glasses and the effect of the crystallization behavior on the roughness and hydrophobicity of the coated surface. Exothermic behavior, including a strong exothermic peak in the 833–972 K temperature range when Fe2O3, TiO2, or Li2O3was added, was confirmed by differential thermal analysis. The modified glass samples (PFTL1–3) showed diffraction peaks when heated at 1073 and 1123 K for 5 min; the crystallized phase corresponds to Fe3(PO4)2, that is, graftonite. We confirmed that the intensity of the diffraction peaks increases at high temperatures and with increasing Li2O3content. In the case of the PFTL3 glass, a Li3Fe2(PO4)2phase, that is, trilithium diiron(III) tris[phosphate(V)], was observed. Through scanning electron microscopy and the contact angles of the surfaces with water, we confirmed that the increase in surface roughness, correlated to the crystallization of the glass frit, increases hydrophobicity of the surface. The calculated values of the local activation energies for the growth of Fe3(PO4)2on the PTFL1, PTFL2, and PFTL3 glass were 237–292 kJ mol−1, 182–258 kJ mol−1, and 180–235 kJ mol−1.

scholarly journals Anti-icing performance of hydrophobic material used for electromechanical drill applied in ice core drilling

2020 ◽  
Vol 66 (258) ◽  
pp. 618-626 ◽  
Author(s):  
Pinlu Cao ◽  
Zhuo Chen ◽  
Hongyu Cao ◽  
Baoyi Chen ◽  
Zhichuan Zheng
Keyword(s):  
Shear Strength ◽  
Ice Core ◽  
Water Repellency ◽  
Contact Angles ◽  
Curved Surface ◽  
Coating Materials ◽  
Water Contact ◽  
Hydrophobic Coating ◽  
Main Challenge ◽  
Ice Adhesion

AbstractUsing an anti-icing coating to prevent ice accretion on the drill surface is a feasible solution to address the drilling difficulties in warm ice. In this study, four types of commercially available hydrophobic coating materials were tested to evaluate their water repellency and anti-icing properties, namely, a mixture of silica and fluorocarbon resin with polytrifluoroethylene, modified Teflon, silica-based emulsion and an acrylic-based copolymer. Their water contact angles are ~107°, 101°, 114° and 95°, respectively. All these hydrophobic coatings can significantly reduce the strength of the ice adhesion within a temperature range of −10 to −30°C on a planar or curved surface. The coating of an acrylic-based copolymer, in particular, can reduce the average tensile strength and the shear strength of the ice adhesion by 87.08 and 97.11% on planar surfaces at −30°C, and by 98.06 and 96.15% on a curved surface, respectively. The main challenge in the practical application of these coatings is their durability. An acrylic-based copolymer coating will lose its water repellency performance after 140 cycles of abrasion. The shear strength of ice adhered on curved surfaces coated with this material will approach that achieved on uncoated surfaces after 11 cycles of icing and de-icing tests.

A Loop Thermosyphon With Hydrophobic Spots Evaporator Surface

2018 ◽  
Author(s):  
Hongbin He ◽  
Biao Shen ◽  
Sumitomo Hidaka ◽  
Koji Takahashi ◽  
Yasuyuki Takata
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Immersion Method ◽  
Two Phase ◽  
Coating Materials ◽  
High Heat Transfer ◽  
Coated Surface

Heat transfer characteristic of a closed two-phase thermosyphon with enhanced boiling surface is studied and compared with that of a copper mirror surface. Two-phase cooling improves heat transfer coefficient (HTC) a lot compared to single-phase liquid cooling. The evaporator surfaces, coated with a pattern of hydrophobic circle spots (non-electroplating Ni-PTFE, 0.5∼2 mm in diameter and 1.5–3 mm in pitch) on Cu substrates, achieve very high heat transfer coefficient and lower the incipience temperature overshoot using water as the working fluid. Sub-atmospheric boiling on the hydrophobic spot-coated surface shows a much better heat transfer performance. Tests with heat loads (30 W to 260 W) reveals the coated surfaces enhance nucleate boiling performance by increasing the bubbles nucleation sites density. Hydrophobic circle spots coated surface with diameter 1 mm, pitch 1.5 mm achieves the maximal heat transfer enhancement with the minimum boiling thermal resistance as low as 0.03 K/W. The comparison of three evaporator surfaces with same spot parameters but different coating materials is carried out experimentally. Ni-PTFE coated surface with immersion method performs the optimal performance of the thermosyphon.

scholarly journals Water modulates the lamellar structure and interlayer correlation of poly(perfluorooctyl acrylate) films: a specular and off-specular neutron scattering study

2021 ◽  
Author(s):  
Akihisa Yamamoto ◽  
Yuji Higaki ◽  
Judith Thoma ◽  
Esther Kimmle ◽  
Ryohei Ishige ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Osmotic Pressure ◽  
Correlation Length ◽  
Ethyl Acrylate ◽  
Contact Angles ◽  
Water Repellent ◽  
Water Molecules ◽  
Coating Materials ◽  
Water Contact ◽  
Vertical Correlation

AbstractComb-like polymers with pendant-like perfluorocarbon side chains self-assemble into smectic lamellae and have been extensively used as water-repellent, hydrophobic coating materials characterized by large water contact angles (θ > 120°). As poly(perfluorooctyl acrylate) films are “apparently hydrophobic” (θ > 120°), the interaction of such materials and water molecules has been largely overlooked. To unravel the molecular-level interactions between water and apparently hydrophobic polymers, specular and off-specular neutron scattering experiments were conducted at defined osmotic pressure ΠH2O. The poly{2-[(perfluorooctylethyl)carbamate]ethyl} acrylate (PFAUr-C8), which had a carbamate linker, transitioned to another lamellar phase at 89 °C. At T = 25 °C; the lamellar periodicity of PFAUr-C8 slightly increased with decreasing osmotic pressure, while the vertical correlation length increased. However, the poly[(perfluorooctyl)ethyl] acrylate (PFA-C8) that did not contain a carbamate linker directly transitioned to a disordered phase at 84 °C. The lamellar periodicity of PFA-C8 was largely independent of the osmotic pressure, suggesting that PFA-C8 was poorly hydrated. Remarkably, the vertical correlation length decreased with decreasing osmotic pressure. Because hydration facilitated by the linker modulated the smectic lamellae of the poly(perfluoroalkyl acrylate), water molecules could be used to optimize the self-assembly of apparently hydrophobic liquid crystalline polymers.

Non-isothermal crystallization behavior of polypropylene/zinc oxide composites

2016 ◽  
Vol 23 (5) ◽  
pp. 505-510 ◽  
Author(s):  
Jianqiang Fang ◽  
Minghua Lang ◽  
Xuchu Ye ◽  
Wei Zhang ◽  
Kongjun Zhu
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Isothermal Crystallization ◽  
Crystallization Behavior ◽  
Crystallization Kinetic ◽  
Exothermic Peak ◽  
Crystallization Time ◽  
Scanning Calorimetry ◽  
Relative Crystallinity ◽  
Oxide Composites

AbstractThe non-isothermal crystallization behavior of polypropylene (PP)/zinc oxide composites with various mass ratios was investigated by differential scanning calorimetry. The Jeziorny and Mo models were applied to calculate the non-isothermal crystallization kinetic parameters of the composites. During non-isothermal crystallization, the width of the exothermic peak increased from 7°C to 12°C with increasing cooling rate. The exothermic peak position at 10°C shifted to a lower temperature, and the half crystallization time t1/2 decreased from 2.86 min to 0.51 min. The Friedman model was used to determine the variation of activation energy at each stage of crystallization. The crystallization activation energies obtained varied significantly at each stage of crystallization. The crystallization activation energy of PP was -126.8 kJ/mol at 70% relative crystallinity but reached -232.8 kJ/mol at 10% relative crystallinity.

scholarly journals Spectral and Thermal Degradation of Melamine Cyanurate

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
V. Sangeetha ◽  
N. Kanagathara ◽  
R. Sumathi ◽  
N. Sivakumar ◽  
G. Anbalagan
Keyword(s):  
Grown Crystal ◽  
Cyanuric Acid ◽  
Average Particle Size ◽  
Exothermic Peak ◽  
Average Particle ◽  
Good Thermal Stability ◽  
Melamine Cyanurate ◽  
Ft Ir ◽  
Diffraction Peaks ◽  
Scherrer Formula

Melamine cyanurate, an organic crystalline complex was, synthesized by evaporation of an aqueous solution containing equimolar quantities of melamine and cyanuric acid. The synthesized compound has been subjected to various characterizations like Powder XRD, FT-IR, TG-DTG, SEM, and SHG. The presence of sharp diffraction peaks in the XRD confirms that the products are highly crystalline. The average particle size was calculated using the Debye-Scherrer formula, and it was found to be 3.067 μm. Thermal behavior of the grown crystal has been studied by TG-DTG analysis. From TG-DTG, it is found that the title crystal possesses good thermal stability. The activation energy was calculated using the Broido, Coats-Redfern, and Horowitz-Metzger methods. A sharp peak exothermic peak at 405.40°C was assigned as the melting point of the title material. SEM reveals the morphology of the synthesized salt. No detectable signal was observed during the Kurtz-Perry technique.

Irradiation of hydrophobic coating materials by gamma rays and protons: space applications

2010 ◽  
Author(s):  
Edward W. Taylor ◽  
Ronald G. Pirich ◽  
John D. Weir ◽  
Dennis Leyble ◽  
Steven Chu ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Coating Materials ◽  
Space Applications ◽  
Hydrophobic Coating

Effect of Wettability on Pool Boiling Incipience in Saturated Water

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jinsub Kim ◽  
Seongchul Jun ◽  
Jungho Lee ◽  
Seong Hyuk Lee ◽  
Seung M. You
Keyword(s):  
Heat Flux ◽  
Life Cycle ◽  
Pool Boiling ◽  
Copper Surface ◽  
Contact Angles ◽  
Al2o3 Nanoparticles ◽  
Saturated Water ◽  
Boiling Incipience ◽  
Coated Surface ◽  
Bare Surface

Three different copper surfaces - bare, Al2O3 nano-coated, and Polytetrafluoroethylene (PTFE) coated - are prepared and tested to examine the effect of wettability on the pool boiling incipience in saturated water at 1 atm. A copper surface is coated with Al2O3 particles ranging 25~43 nm in diameter by immersing the surface in Al2O3/ethanol nanofluid (1g/l) and boiled for 3 min. SEM image in Fig. 1 shows the coated Al2O3 nanoparticles on the copper surface, together with the reference bare surface. PTFE coating is also applied to the copper surface using spin coating method with the mixture of Dupont AF 2400 particles and 3M FC-40 solvent. The final coating thickness of the PTFE coating is estimated to be 30 nm. The three surfaces exhibit different static contact angles, 78° (bare), 28° (nano-coated), and 120° (PTFE coated) in Fig. 2, respectively. Wettability affects the boiling incipience heat flux where initial bubble nucleation starts: 15 kW/m2 for the bare surface; 30 kW/m2 for the nano-coated surface; and 2.5 kW/m2 for the PTFE coated surface. Captured images from the high speed camera at 2,000 fps show significantly different bubble shapes and departure frequencies in Fig. 3. During the bubble growth, advancing contact angles are captured and shown qualitatively and found consistent with their static angle measurements for the sessile droplet observed at each surface. The larger bubble is generated on the nano-coated surface compared to that of the bare surface because improved wetting makes promising cavities flood and thus incipience is delayed, resulting in higher superheat. The single bubble life cycle appears to be much longer on the PTFE coated surface due to the increase of the contact angle which becomes hydrophobic (> 90°), resulting in lower bubble departure frequency. Successive tests at the same heat flux of 30 kW/m2 confirmed that life cycle on the PTFE coated surface (88.5 ms) is consistently longer than that on the bare surface (16.5 ms) and nano-coated surface (20 ms).

scholarly journals The Analysis of Periodic Order in Monolayers of Colloidal Superballs

2021 ◽  
Vol 11 (11) ◽  
pp. 5117
Author(s):  
Daniël N. ten Napel ◽  
Janne-Mieke Meijer ◽  
Andrei V. Petukhov
Keyword(s):  
Form Factor ◽  
Colloidal Particles ◽  
Bragg Diffraction ◽  
General Strategy ◽  
X Ray Scattering ◽  
Coated Surface ◽  
Diffraction Peaks ◽  
Diffraction Patterns ◽  
Low Dimensional

The characterization of periodic order in assemblies of colloidal particles can be complicated by the coincidence of Bragg diffraction peaks of the structure and minima in the form factor of the particles. Here, we demonstrate a general strategy to overcome this problem that is applicable to all low-dimensional structures. This approach is demonstrated in the application of small-angle X-ray scattering (SAXS) for the characterization of monolayers of colloidal silica superballs prepared using the unidirectional rubbing method. In this method, the ordering of the colloidal superballs is achieved by mechanically rubbing them onto a polydimethylsiloxane (PDMS)-coated surface. Using three differently shaped superballs, ranging from spherical to almost cubic, we show that certain Bragg peaks may not appear in the diffraction patterns due to the presence of minima in the form factor. We show that these missing Bragg peaks can be visualized by imaging the colloidal monolayers at various orientations. Moreover, we argue that the same strategy can be applied to other techniques, such as neutron scattering.

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