•Anti-icing property is related to wettability and surface roughness.•Silicone based hydrophobic coating showed excellent ice-adhesion strength.•Superhydrophobic surfaces displayed poor anti-icing ...property.
The anti-icing properties of hydrophilic, hydrophobic and superhydrophobic surfaces/coatings were evaluated using a custom-built apparatus based on zero-degree cone test method. The ice-adhesion reduction factor (ARF) of these coatings has been evaluated using bare aluminium alloy as a reference. The wettability of the surfaces was evaluated by measuring water contact angle (WCA) and sliding angle. It was found that the ice-adhesion strength (τ) on silicone based hydrophobic surfaces was ∼ 43 times lower than compared to bare polished aluminium alloy indicating excellent anti-icing property of these coatings. Superhydrophobic coatings displayed poor anti-icing property in spite of their high water repellence. Field Emission Scanning Electron Microscope reveal that Silicone based hydrophobic coatings exhibited smooth surface whereas the superhydrophobic coatings had a rough surface consisting of microscale bumps and protrusions superimposed with nanospheres. Both surface roughness and surface energy play a major role on the ice-adhesion strength of the coatings. The 3D surface roughness profiles of the coatings also indicated the same trend of roughness. An attempt is made to correlate the observed ice-adhesion strength of different surfaces with their wettability and surface roughness.
► ZnO:Cu nano particles are prepared via solution combustion technique with ODH fuel at low temperature. ► Analysis of X-ray line broadening and micro strain in nanoparticles are evaluated using W-H ...plots. ► PXRD results confirm that the nanopowders exhibit hexagonal wurtzite structure. ► Decrease in the green emission and enhancement of UV emission in Cu doped ZnO due to the decrease in defects. ► EPR spectrum exhibits a broad resonance signal at
g
∼
2.049 and two narrow resonances one at
g
∼
1.990 and other at
g
∼
1.950.
Cu (0.1
mol%) doped ZnO nanopowders have been successfully synthesized by a wet chemical method at a relatively low temperature (300
°C). Powder X-ray diffraction (PXRD) analysis, scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectroscopy, UV–Visible spectroscopy, Photoluminescence (PL) and Electron Paramagnetic Resonance (EPR) measurements were used for characterization. PXRD results confirm that the nanopowders exhibit hexagonal wurtzite structure of ZnO without any secondary phase. The particle size of as-formed product has been calculated by Williamson–Hall (W–H) plots and Scherrer's formula is found to be in the range of ∼40
nm. TEM image confirms the nano size crystalline nature of Cu doped ZnO. SEM micrographs of undoped and Cu doped ZnO show highly porous with large voids. UV–Vis spectrum showed a red shift in the absorption edge in Cu doped ZnO. PL spectra show prominent peaks corresponding to near band edge UV emission and defect related green emission in the visible region at room temperature and their possible mechanisms have been discussed. The EPR spectrum exhibits a broad resonance signal at
g
∼
2.049, and two narrow resonances one at
g
∼
1.990 and other at
g
∼
1.950. The broad resonance signal at
g
∼
2.049 is a characteristic of Cu
2+ ion whereas the signal at
g
∼
1.990 and
g
∼
1.950 can be attributed to ionized oxygen vacancies and shallow donors respectively. The spin concentration (
N) and paramagnetic susceptibility (
χ) have been evaluated and discussed.
•Superhydrophobic coatings using PVDF/MWCNT have been prepared.•Effects of MWCNT and temperature on wettability have been studied.•Transformation of hydrophobic to superhydrophoic state is achieved ...with CNT content.•After 573K superhydrophobic to superhydrophilic state is achieved.•Advantage is feasibility for application over large area and is stable upto 573K.
Thermally stable superhydrophobic coatings have been prepared using polyvinylidene fluoride (PVDF)–multiwalled carbon nanotubes (MWCNTs) by spray coating method. The effects of MWCNT (0–66wt.%) and temperature (300–623K) on wettability have been studied. A transformation from hydrophobic to superhydrophoic state has been achieved with increase of CNT content. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies reveal that with increase in CNT content, α-phase of PVDF decreases suggesting that MWCNT has strong effect on the phase separation of PVDF. Field emission scanning electron microscopy (FESEM) studies show that the coatings have rough surface with porous structure. With increase in MWCNT content the protrusion like structures decrease that leads to micro/nano scales. The coatings are thermally stable up to 573K exhibiting superhydrophobicity and thereafter transformed to superhydrophilic state at 623K. Energy dispersive X-ray spectroscopy (EDXS) analysis shows the absence of fluorine after annealing at 623K suggesting decomposition of PVDF. X-ray photoelectron spectroscopy (XPS) of C1s and F1s core levels in as-deposited PVDF–MWCNT coating show the presence of CF2 related species. Concentration of fluorine drastically decreases after heat treatment of the coating at 623K. The main advantage of the present method is feasibility for application over large area and the coatings are stable up to 573K.
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•Y2O3 for photo- and thermo-luminescent applications is synthesized by combustion route.•Luminescence property is tuned for different applications by using a suitable fuel.•Influence ...of fuel on structural and luminescence characteristics of Y2O3 is explored.•Possible reasons for the observed spectral characteristics are discussed in detail.
We present a simple route for synthesis of Y2O3 for both photoluminescent (PL) and thermoluminescent (TL) applications. We show that by simply switching the fuel from ethylene di-amine tetracetic acid (EDTA) to its disodium derivative (Na2-EDTA), we obtain a better photoluminescent material. On the other hand, use of EDTA aids in formation of Y2O3 which is a better thermoluminescent material. In both cases pure cubic nano-Y2O3 is obtained. For both the material systems, structural characterization, photoluminescence, thermoluminescence, and absorbance spectra are reported and analyzed. Use of EDTA results in nano Y2O3 with crystallite size ∼10nm. Crystallinity improves, and crystallite size is larger (∼30nm) when Na2-EDTA is used. TL response of Y2O3 nanophosphors prepared by both fuels is examined using UV radiation. Samples prepared with EDTA show well resolved glow curve at 140°C, while samples prepared with Na2-EDTA shows a glow curve at 155°C. Effect of UV exposure time on TL characteristics is investigated. The TL kinetic parameters are also calculated using glow curve shape method. Results indicate that the TL behavior of both the samples follow a second order kinetic model.
► Superhydrophobic (SH) surfaces based on ZnO–PDMS nanocomposite coatings are demonstrated by wet chemical method. ZnO coating exhibits wetting behaviour with WCA of ∼108°, on modification with PDMS, ...it transforms to superhydrophobic surface ∼155°. ► FESEM micrographs reveal that nanoparticles are connected to each other to make large network systems consisting of hierarchical structure. ► EPR studies on SH coatings revealed that the surface defects play a major role on the wetting behaviour. Advantages of the present method include the cheap and fluorine-free raw materials, environmentally benign solvents, and feasibility for applying on large area of different substrates.
Superhydrophobic surfaces based on ZnO–PDMS nanocomposite coatings are demonstrated by a simple, facile, time-saving, wet chemical route. ZnO nanopowders with average particle size of 14
nm were synthesized by a low temperature solution combustion method. Powder X-ray diffraction results confirm that the nanopowders exhibit hexagonal wurtzite structure and belong to space group
P63
mc. Field emission scanning electron micrographs reveal that the nanoparticles are connected to each other to make large network systems consisting of hierarchical structure. The as formed ZnO coating exhibits wetting behaviour with Water Contact Angle (WCA) of ∼108°, however on modification with polydimethylsiloxane (PDMS), it transforms to superhydrophobic surface with measured contact and sliding angles for water at 155° and less than 5° respectively. The surface properties such as surface free energy (
γ
p), interfacial free energy (
γ
pw), and the adhesive work (
W
pw) were evaluated. Electron paramagnetic resonance (EPR) studies on superhydrophobic coatings revealed that the surface defects play a major role on the wetting behaviour. Advantages of the present method include the cheap and fluorine-free raw materials, environmentally benign solvents, and feasibility for applying on large area of different substrates.
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► A ZnO nanopowder by LSC method with ODH as a fuel is reported for the first time. ► PXRD, SEM, TEM, FTIR, UV–Vis, Raman, PL, TL and EPR studies were carried out. ► We report for ...first time TL properties of ZnO nanopowders irradiated by γ-rays. ► Trapping parameters with various γ- doses are calculated using peak shape method.
Spherical shaped ZnO nanopowders (14–50
nm) were synthesized by a low temperature solution combustion method in a short time <5
min. Rietveld analysis show that ZnO has hexagonal wurtzite structure with lattice constants
a
=
3.2511(1)
Å,
c
=
5.2076(2)
Å, unit cell volume (
V)
=
47.66(5) (Å)
3 and belongs to space group P63mc. SEM micrographs reveal that the particles are spherical in shape and the powders contained several voids and pores. TEM results also confirm spherical shape, with average particle size of 14–50
nm. The values are consistent with the grain sizes measured from Scherrer's method and Williamson–Hall (W–H) plots. A broad UV–vis absorption spectrum was observed at ∼375
nm which is a characteristic band for the wurtzite hexagonal pure ZnO. The optical energy band gap of 3.24
eV was observed for nanopowder which is slightly lower than that of the bulk ZnO (3.37
eV). The observed Raman peaks at 438 and 588
cm
−1 were attributed to the E
2 (high) and E
1 (LO) modes respectively. The broad band at 564
cm
−1 is due to disorder-activated Raman scattering for the A
1 mode. These bands are associated with the first-order Raman active modes of the ZnO phase. The weak bands observed in the range 750–1000
cm
−1 are due to small defects.
•Ec of MgAl2O4 spinel glass–ceramics has been found to be 250–270kJ/mol.•TEM images show presence of cubic crystals of uniform size 10–15nm in the GC.•HV ∼6.0GPa, Kc∼5.0MPam1/2, flexural strength ...∼100MPa and E∼55GPa obtained.•Observed red emission of Cr3+ ions due to spin-forbidden 2Eg→4A2g transition.
The mechanical, thermal, and optical properties, along with the microstructure and electron paramagnetic resonance (EPR) spectra, have been studied for MgAl2O4:Cr3+ spinel glass and glass–ceramics. The activation energy of the crystallization has been estimated from the differential scanning calorimetry (DSC) study using different models and is found to vary within 255–270kJ/mol for the un-doped precursor glass. The microstructure of the glass–ceramics has been characterized using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The TEM images demonstrate the presence of cubic crystals in the glass–ceramics of uniform size 10–15nm. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy reveal the presence of MgAl2O4 spinel as the only crystalline phase, formed in the heat-treated glass–ceramics. The EPR spectrum of Cr3+ doped glass sample exhibits a broad resonance signal with effective g=1.97 whereas in glass–ceramic sample an additional weak resonance signal is observed at g=3.83. The excitation spectrum exhibits two bands in the visible region. The emission spectrum exhibits an intense red emission at 690nm which is characteristic of Cr3+ ions caused by the spin-forbidden 2Eg→4A2g transition. All the mechanical properties are found to have improved in the glass–ceramics when compared to glasses. A good combination of micro-hardness (∼6.0GPa), high fracture toughness (∼5.0MPam1/2), 3 point flexural strength (∼100MPa) and elastic modulus (∼55GPa) has been obtained for the glass–ceramic samples.
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•The β-Ca2SiO4:Eu3+ (1–5mol%) phosphors prepared using low temperature combustion method.•XRD, SEM and FTIR techniques used to characterize the phosphor.•TL and PL properties were ...well studied.•Prepared phosphor may be used for making the white LEDs and dosimetric applications.•The color purity has been verified by using the chromaticity diagram.
Nanocrystalline Ca2SiO4:Eu3+ (1–5mol%) phosphors have been prepared by solution combustion process using DFH as a fuel which is less temperature compared to solid state route. The powders were well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. PXRD results confirm the β-Ca2SiO4 phase upon calcination at 950°C for 3h. SEM micrographs indicate that the product is highly porous and agglomerated particles. Thermoluminescence (TL) studies have been carried out with γ-irradiation in the dose range 1–6kGy. Two TL glow peaks are recorded at ∼439 and ∼536K for all the Eu3+ concentrations (1–5mol%), the highest TL glow peak intensity was recorded for 4mol% Eu3+. The 439K glow peak increases linearly with γ-dose whereas, 536K glow peak follows sublinear. The kinetic parameters (E, b, s) have been estimated from different methods. Further, 439K TL glow peak show good linearity, hence it is quite useful in radiation dosimetry. The PL spectra consists of series of peaks at 565–580, 590, 613–618, 652–681nm respectively upon excited at different excitation wavelengths. These peaks are attributed to the transitions 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F2, 5D0→7F3 and 5D0→7F4 respectively. The chromaticity co-ordinates of the Eu3+ activated samples are located in white light and hence the phosphor is highly useful for white LED’s.
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