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Magnesium (Mg) alloys have a high strength/weight ratio, high dimensional stability, good machinability, and the ability to be recycled. However, their poor corrosion resistance in humid environments limits their usage for exterior aerospace components. This study aims to improve the corrosion resistance of two Mg alloys (AZ31B and AZ91) by using aluminum coatings. The latter have been deposited by a low pressure and temperature cold spray process. An aluminum powder (60 wt%) with a particle size ranging between 1 and 8 µm and nickel powder (40 wt%) with a particle size of about 70 µm were blended and used as feedstock powder. The coating thickness was about 240 μm. Its densification was achieved by the in-situ hammering effect of the nickel particles. The shot-peening effect also resulted in an enhanced coating hardness. The microstructure, mechanical properties, and corrosion resistance of the coatings have been investigated. They showed that the aluminum had a face centered cubic structure. Potentiodynamic polarization tests were performed along with a combination of materials characterization techniques to assess the corrosion resistance of the coatings when immersed in a 3.5 wt% NaCl solution for long durations. The results revealed that the corrosion resistance increased with the immersion time because of the formation of a protective oxide layer on the surface. These results were supported by elemental and structural analyses. This study shows that cold-sprayed aluminum coatings are a promising candidate for enhancing the corrosion resistance of AZ31B and AZ91Mg alloys compared to other thermal spray processes.

The tribo-mechanical properties of NiMoAl-Cr2AlC MAX phase composite coatings on stainless steel substrate have been investigated. NiMoAl with different amounts of Cr2AlC (10, 20, 50 and 100 wt.%) were prepared by turbo-mixing and deposited by High-Velocity Oxy-Fuel (HVOF) method on stainless steel substrate. The phase composition, microstructure, chemical composition, tribological and mechanical properties of the coatings were analyzed using x-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy-Dispersive x-ray analysis (EDAX), pin-on-disk wear testing rig and nanohardness tester, respectively. The worn surfaces were analyzed by metallurgical optical microscope, FESEM and three-dimensional surface profiler to understand the wear behavior in detail. The addition of the Cr2AlC MAX phase in NiMoAl enhances the mechanical properties and reduces the surface roughness and porosity. NiMoAl-20 wt.% Cr2AlC and Cr2AlC coatings containing equal amounts of oxygen and carbon in the tribofilm show the low coefficient of friction (COF) and wear rate. The addition of the Cr2AlC MAX phase in the NiMoAl matrix up to 20 wt.% reduces the wear rate by one order of magnitude and enhances the coating life by 7000 twist fatigue cycles.

The aim is to deposit Ni-Mullite (70:30 wt%) coating on mild steel (MS) by high velocity oxy-fuel (HVOF) thermal spray process. The spraying conditions have been optimized to obtain an adherent coating of ∼110 µm thickness. The coated specimens of dimensions (20mmx20mm) had been subjected to atmospheric oxidation at different temperatures of 500°, 700°, 900° and 1000 °C. Oxidation was performed for durations of 5, 18, 30 and 45 h. The oxidized coatings have been characterized by X-Ray Diffraction (XRD) and Energy Dispersive Spectroscopy (EDAX). The oxidation rate has been studied in terms of mass gain with respect to time and temperature. It has been seen that till 700 °C, there is negligible change in the mass gain and the oxide layer thickness. Beyond 700 °C the mass gain and thickness of the oxide layer increases considerably upto a temperature of 1000 °C. The growth of the oxidized zone is seen to obey the parabolic law at high temperatures. Field Emission Scanning Electron Microscopy (FESEM) had been used to analyse the surface morphology. The as-coated specimen revealed the formation of porous nickel oxide with mullite particles distributed as fine nodular morphology. However, in oxidized specimens, formation of uniform grains containing aggregates of oxides of iron and that of wurtzite and haematite had been observed. This was also confirmed from EDAX analysis. The formation of iron oxide can be associated with the fact that iron diffuses outward to the surface resulting in oxide formation. This was reflected in the X-ray diffractogram as the highest intensity peaks in the oxidized specimen. This depicts that top surface has facilitated the oxidation of the base metal by the outward diffusion of iron atoms. Thus, to make this coating suitable for use at high temperatures, an interlayer that prevents interdiffusion of elements between the substrate and coating is required.

The aim of the present study is to develop thermally sprayable WC-12Co and WC-12Co-xAl2O3 (x = 10 and 15 wt.%) cermet coatings on steel substrate (SS 304) by high-velocity oxy fuel (HVOF) method. Influence of Al2O3 addition on the wear and corrosion behavior of WC-12Co coating has been studied. The microstructure and chemical composition of the coatings were analyzed using field emission scanning electron microscope (FESEM), and phase identification was carried out using x-ray diffraction (XRD) studies. The morphology of the coating appears as coarse granular structure. The XRD studies revealed the presence of hexagonal WC phase along with η-Co6W6C phase. It has been observed from the microhardness measurements, that the values gradually increase from 950 to 1300 HK with the addition of Al2O3 from 0 to 15 wt.%. The wear rate of WC-12Co-15Al2O3 (3.19 × 10−6 mm3/Nm) and WC-12Co-10Al2O3 (5.26 × 10−6 mm3/Nm) coatings was seen to be one order of magnitude lower than that of WC-12Co (2.9 × 10−5 mm3/Nm) coating. The polarization studies revealed that WC-12Co-15Al2O3 cermet coating showed superior corrosion protection than that of WC-12Co-10Al2O3 and WC-12Co coatings. This has been attributed to the gradual decrease in the porosity levels with an increase in Al2O3 content which is supported by morphology studies. The microhardness and wear behavior of WC-12Co-Al2O3 coatings are equivalent to those of hard chrome suggesting the possibility of its replacement.

Effect of thermal aging and chemical treatment on the physical properties of coir fiber was investigated. Coir fibers were treated with sodium hydroxide and glutaraldehyde for 2 h. The influence of alkali and aldehyde treatment on tensile strength and elongation at break was studied in detail. Enhancement in tensile strength of coir fiber was observed up to five days of aging at 50°C and further decreased. Thermal cross linking of cellulose present in the fiber may be the reason for the increase in tensile strength and thermal degradation due to the chain scission of cellulose reduced the tensile strength. Sodium-hydroxide-treated samples showed an increase in tensile strength and reduction in elongation at break. The removal of impurities such as waxy and fatty acid residues from the coir fiber by reacting with strong base solution improved the strength of fiber. Cross linking of cellulose with glutaraldehyde in the fiber reduced the elasticity and enhances the strength of the material. Scanning ...

Glasses with compositions xV(2)O(5) - (100 - x)0.8NaPO(3) - 0.2ZnO] (where 0.2

A manganese based spinel ferrite, chemically modified with polymethyl methacrylate (PMMA) and polyaniline (PANI) are synthesized and their composites are used as electromagnetic interference (EMI) shielding materials. X-ray diffraction studies show that the as-prepared manganese ferrite crystallizes in a cubic spinel structure. The particles are highly agglomerated and nanocrystalline as indicated by transmission electron microscopy. Manganese exists in +2 and +4 oxidation states and Fe in +2 and +3 oxidation states. Modified manganese ferrite and polyaniline composites in different weight ratios are evaluated for their EMI shielding properties. It is observed that composites containing the PMMA modified ferrite show enhanced total shielding effectiveness (SE T ) compared to those containing the unmodified ferrite in the X band frequency range (8-12 GHz). The optimized ratio of the PMMA modified ferrite and PANI demonstrates SE T values as high as �44 dB in the X band frequency range. © the Owner Societies.

Optically transparent hydrophobic and superhydrophobic coatings have been prepared using polyamide 12–SiO2 nanocomposite (NC) on glass substrates by the spin-coating method. The coatings have been optimized for their hydrophobicity and transparency. The transformation from hydrophobic to superhydrophobic is achieved with increase in roughness (Ra) which increases with SiO2 content. These coatings are highly transparent in the entire visible region (400–800 nm). The influence of layer thickness on water contact angle (WCA) and optical transmittance of the coatings has been studied. Field emission scanning electron micrograph (FESEM) shows the presence of SiO2 nanoparticles covered with polyamide homogenously on the surface and the particles are aggregated to form a rough structure. X-ray diffraction (XRD) patterns show that the polyamide losses its crystalline structure in the composite. The preparation procedure reported here is simple and eco-friendly. The dual nature of the coatings, that is, high transparency and superhydrophobicity in the entire visible region suggests for its potential usage in self-cleanings, wind screen and optoelectronic applications. Copyright © 2016 John Wiley & Sons, Ltd.

Cost effective and low temperature synthesis methods namely solution combustion and hydrothermal methods were used to prepare chromium incorporated nanocrystalline zinc ferrites. The effect of incorporation of low concentration Cr3+ ions on the structural, morphological, magnetic and transport properties of the zinc ferrite compounds were investigated. The crystalline nature and size variation with chromium content were valid from powder x-ray diffraction. Particles size and crystallite size variation were valid from scanning electron microscopy and transmission electron microscopy respectively. With the increase in chromium incorporation, the crystallite and particles sizes were decreased. Fourier transform infrared spectroscopy (FTIR) studies confirmed the presence of strong metal-oxygen bonds. The elastic properties of the materials in both the methods were estimated by FTIR studies. Magnetic properties namely saturation magentization, remanent magnetization and coercivity values were decreased with increase in Cr3+ ions concentration. The dielectric properties of the samples decreased with increase in the Cr3+ ions. The dielectric constant was observed to be of the order of 10(6) at low frequency and almost 1 at higher frequency range. The activation energy estimated using Arrhenius plots was of the order of 0.182 eV and 0.368 eV respectively for the compounds prepared by solution combustion and hydrothermal methods. The emission spectra of the samples excited at 344 nm were reported using photoluminescence (PL) spectroscopy. Further, the approximate energy band gap(E-g) was estimated from PL studies. The E-g of the materials were lie in the range of 2.11-1.98 eV. (C) 2015 Elsevier B.V. All rights reserved.

One-dimensional (1D) zinc oxide (ZnO) hexagonal rods have been successfully synthesized by surfactant free hydrothermal process at different temperatures. It can be found that the reaction temperature play a crucial role in the formation of ZnO uniform hexagonal rods. The possible formation processes of 1-D ZnO hexagonal rods were investigated. The zinc hydroxide acts as the morphology-formative intermediate for the formation of ZnO nanorods. Upon excitation at 325 nm, the sample prepared at 180 °C show several emission bands at 400 nm (∼3.10 eV), 420 nm (∼2.95 eV), 482 nm (∼2.57 eV) and 524 nm (∼2.36 eV) corresponding to different kind of defects. TL studies were carried out by pre-irradiating samples with γ-rays ranging from 1 to 7 kGy at room temperature. A well resolved glow peak at ∼354 °C was recorded which can be ascribed to deep traps. Furthermore, the defects associated with surface states in ZnO nano-structures are characterized by electron paramagnetic resonance.

CdSiO 3 :Eu 3+ (0.5–5 mol%) nanophosphors were synthesized using oxalyl di-hydrazide fuel by solution combustion technique for the first time . The structural, thermo and photoluminescent properties were studied. The average particle size was estimated from transmission electron microscopy (TEM) studies and found to be in the range 20–30 nm. The values were in good agreement with Scherer’s method and Williamson–Hall plots. Scanning electron microscope (SEM) showed highly porous, fluffy and many agglomerated particles. Photoluminescence (PL) CdSiO 3 :Eu 3+ (0.5–5 mol%) shows emission peaks at 577, 596, 612, 659 and 706 nm which were assigned to 5 D 0 → 7 F j (j = 0, 1, 2, 3, 4) transition respectively. It was observed that PL intensity increases up to the concentration 4 mol% Eu 3+ . Thermoluminescence (TL) studies were carried out on CdSiO 3 :Eu 3+ (1–5 mol%) nanophosphor by exposing to γ-rays (1–6 kGy) and UV (5–25 min) respectively. The TL intensity was found to be highest in 1 mol% Eu 3+ concentration. Further, effect of different gamma (1–6 kGy) and UV (5–25 min) exposure was studied on CdSiO 3 :Eu 3+ nanophosphor. Simple well resolved glow peak at ∼178 °C was recorded for both the exposures. The TL intensity at 178 °C increase linearly with increase in the γ-dose. However, in UV exposed samples the TL glow peak intensity increase up to 10 min and thereafter the peak intensity decreases with further increase in exposure time. The effect of heating rate (β) and fading characteristics for γ and UV were studied in CdSiO 3 :Eu 3+ (1 mol%). The kinetic parameters ( E , b , s ) were estimated using different theoretical methods.

The present study aims to develop dense FeCoCrNi2Al high entropy alloy (HEA) coating of thickness ≅ 200 μm by high velocity oxy-fuel (HVOF) process. Studies on the microstructure and mechanical properties like microhardness, erosion resistance of the HVOF coated FeCoCrNi2Al HEA has not been reported by any investigator. An adherent coating has been deposited displaying a lamellar microstructure. The X-ray diffractogram of the coating revealed the formation of a major FCC and a minor BCC phase with small amount of oxide. The oxide phase was confirmed to be Al2O3 using Raman spectroscopy. The microhardness of the coating is found to be 600 ± 30 VHN with no crack formation upto a load of 1 kgf. The erosion resistance of the HEA coated steel was evaluated upto a temperature of 800 °C. The coating displays good erosion resistance and the depth of penetration of the erodent was well within the coating thickness with no delamination of the coating, thereby making it suitable for high temperature applications.

Mn doped MgO Nanoparticles have been prepared by Solution Combustion Synthesis. The synthesized sample is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Paramagnetic Resonance (EPR). The prepared MgO:Mn (1 mol%) nano crystals appear to be of simple cubic crystalline phase with lattice parameters a = 4.218(2) A and cell volume = 74.98 (7) A3. SEM micrograph of powders show highly porous, many agglomerates with irregular morphology, large voids, cracks and pores. EPR spectrum of the sample at room temperature exhibit an isotropic sextet hyperfine pattern, centered at g=1.99, characteristic if Mn2+ ions with S=I=5/2.The observed g value and the hyperfine value reveal the ionic bonding between Mn2+ and its surroundings.