Generation of nanocrystalline NiO particles by solution combustion method and its Zn?NiO composite coating for corrosion protection

The nanocrystalline nickel oxide (NiO) particles have been successfully prepared by a simple, fast, economical, and eco‐friendly solution‐combustion method using Ni(NO₃)₂ · 6H₂O (oxidizer) and sugar (dextrose as fuel). The as‐prepared compound was calcined for an hour at different temperatures. The synthesized NiO was characterized by XRD, TGA, SEM/EDX, TEM, XPS, FT‐IR, and UV–Vis spectral methods. The crystallite sizes of the NiO particles were measured. Rietveld refinement of X‐ray data matches the cubic structure with space group of Fm3m (No. 225). The thermal behavior of as‐prepared compound was examined. Scanning electron micrographs show uniform cubic like morphology of NiO and its chemical composition was measured. The TEM results reveal that the particle sizes were in the order of 70–80 nm. The red shift was noticed in UV–Vis absorption spectra. As an application part the Zn? NiO composite coating was prepared by electrodeposition method and its corrosion behavior was analyzed by Tafel, impedance and anodic polarization in aggressive medium.     

Synthesis and characterization of novel graft copolymers of Poly(N-vinylcarbazole) and Poly(3-methylthiophene) for optoelectronic applications

In this paper, we report the synthesis and characterization of a new material based on Poly(N-vinylcarbazole) (PVK) and Poly(3-methylthiophene) (PMeT), which has been chemically prepared by cross-linking of PVK in the presence of 3-methylthiophene monomers in chloroform with anhydrous FeCl₃. Thus, two samples were prepared, PVK–3MeT1 and PVK–3MeT2, obtained firstly in the fully doped state and successfully dedoped by chemical treatment. They were characterized by various spectroscopic methods as well as thermal analysis and conductivity measurements. Then, the formation of PMeT by oxidative coupling and its grafting into the skeleton of PVK is shown. Furthermore, the optical analysis shows that the new materials exhibit a blue-shift compared to that of the PMeT homo-polymer. The obtained graft copolymer presents interesting optical and thermal properties compared to that of the homo-polymers.     

Novel packing type of ET radical cation layers in a new organic conductor (ET)5[Dy(NCS)6NO3]·C2H5OH with a metal-complex lanthanide anion

A new radical cation (ET)₅[Dy(NCS)₆NO₃]·C₂H₅OH salt was prepared by electrochemical oxidation of ET in a chlorobenzene–ethanol solution. Its crystal structure and conducting properties were examined. The salt has a layered crystal structure with a basically new packing type of the radical cation layer, which was called an ω-type. Resistance studies reveal a semiconducting nature of this salt.     

Microstructural,mechanical and shape memory characterizations of Ti–Mo–Sn alloys

As a β stabilizing element in Ti-based alloys, the effect of Mo on phase constitution, microstructure, mechanical and shape memory properties was investigated. Different compositions of Ti–xMo–3Sn alloys (where x=2, 4, 6, at.%) were prepared by arc melting. A binary composition of Ti–6Mo alloy was also prepared for comparison. Ti–xMo–3Sn alloys show low hardness and high ductility with 90% reduction in thickness while Ti–6Mo alloy shows high hardness, brittle behavior, and poor ductility. Field emission scanning electron microscopy (FESEM) reveals round morphology of athermal ω (ω_ath) precipitates. The presence of ω_ath phase is also confirmed by X-ray diffraction (XRD) in both as-cast and solution-treated and quenched conditions. The optical microscopy (OM) and FESEM show that the amount of martensite forming during quenching decreases with an increase in Mo content, which is also due to β→ω transformation. The hardness trends reinforce the presence of ω_ath too. The shape memory effect (SME) of 9% is the highest for Ti–6Mo–3Sn alloy. The SME is trivial due to ω_ath phase formation; however, the increase in SME is observed with an increase in Mo content, which is due to the reverse transformation from ω_ath and the stress-induced martensitic transformation. In addition, a new and very simple method was designed and used for shape memory effect measurement.     

Microstructure,mechanical properties and oxidation behavior of powder compacts of the Nb–Si–B system prepared by spark plasma sintering

Powder compacts with eight different compositions in the Nb–Si–B system were prepared by spark plasma sintering and their microstructure, mechanical properties and oxidation behavior were investigated. Oxidation resistance of Nb₅Si₃B₂ compacts is better than that of Nb₅Si₃ compacts, but extremely poorer than that of NbSi₂ compacts. However, since the oxidation experiment was of short duration, details of the oxidation behavior of Nb–Si–B compacts have yet to be investigated. Compacts were prepared via the following three different routes: (i) elemental powders were mixed in a rotational ball mill and then consolidated by spark plasma sintering method, (ii) elemental powders were mechanically alloyed and consolidated similarly to (i) and (iii) pulverizing compacts prepared via route (i) and consolidated once again similarly to (i). Compacts prepared via the third route exhibit more homogeneous microstructures and contain a smaller amount of SiO₂ than compacts prepared via the other two routes. Compacts with compositions around the line of Nb₅Si₃–Nb₅Si₃B₂–NbB₂ exhibit a high hardness at room temperature and a high compressive strength at high temperatures in comparison to those with compositions away from the line. The strength of compacts containing NbSi₂ decreases with increasing the volume fraction of NbSi₂ phase.     

Aliphatic–aromatic poly(azomethine)s with ester groups as thermotropic materials for opto(electronic) applications

We have explored the opto(electronic) and liquid crystal properties of a new series of semiconducting materials based on aliphatic–aromatic poly(azomethine)s. The structures of polymers were characterized by means of FTIR, ¹H, ¹³C NMR spectroscopy, and elemental analysis. UV–vis properties of the thin films of the polymers were investigated on the quartz substrate. The lowest optical energy gap (E_g) at 2.28 eV was found. The polymers were irradiated with a test dose of 2 Gy Co-60 gamma-rays to detect their thermoluminescence properties in the temperature range 25–200 °C. Mesomorphic behavior was investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) studies. Being into consideration backbone geometry, all polymers, excepted polymer PAZ2, obtained from poly(1,4-butanediol)bis(4-aminobenzoate) and 9-(2-ethylhexyl)carbazole-3,6-dicarboxaldehyde, exhibited liquid-crystalline properties. Moreover, the electrical characterizations of bulk heterojunction (BHJ) and bilayer devices with the following architecture ITO/PEDOT/PAZ:TiO₂/Al were investigated. Additionally, devices without and with TiO₂ layer such as ITO/PAZ/Al and ITO/TiO₂/PAZ/Al were prepared and investigation in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layers and powders. Moreover, impedance spectroscopy at different temperatures for electrical properties measurement was used. Additionally, the compounds were tested using various AFM techniques such as Mode and Phase Imaging and local contrast force–distance curve measurement and roughness (Ra, Rms) along with skew and kurtosis are presented.     

Chemical aspects of plasma spraying of zirconia-based thermal barrier coatings

Zirconia-based thermal barrier coatings (TBCs) of nominal chemical composition 8 wt.% Y₂O₃–ZrO₂ and 25.5 wt.% CeO₂–2.5 Y₂O₃–ZrO₂ were prepared by atmospheric plasma spray and low-pressure plasma spray by selecting different deposition parameters. The surface chemical composition has been investigated by X-ray photoelectron spectroscopy in order to study the variation of surface chemical composition induced by the plasma-spraying process as a function of deposition parameters. The results reveal the occurrence of chemical–physical reactions such as stabilizing oxide depletion and enrichment, reduction to lower valence states, impurity segregation phenomena and the formation of new species. The chemical information was confirmed by differential thermal analysis measurements, which indicates that chemical aspects in plasma spraying are relevant and should be considered in designing reliable TBCs for maximum performance in aerospace applications.     

Effect of remelting process on characterization of air-plasma sprayed Fe67.5Ni23.5B9 alloy coatings onto 1Cr18Ni9Ti stainless steel

To develop a composite material with good mechanical and radiation shielding properties, the Fe–Ni–B (Fe_67.5Ni_23.5B₉, wt. %) coatings onto ₁Cr₁₈Ni₉Ti stainless steel substrate (SS, same as below) were prepared using air-plasma spraying (APS) technique in this work. A remelting process (1050 °C/2 h) was performed on the Fe–Ni–B coatings laminated composite under vacuum condition. The microstructure, phase composing, adhesion strength, Vickers hardness distribution and residual stress of Fe–Ni–B coatings before and after the remelting process were contrastively characterized. The results show that the remelting process decrease the coating defects and make the coating more cohesive and stable. The element diffusion and new compounds formation within the coating and interface area improves the adhesion and thermal fatigue of Fe–Ni–B coatings. In addition, the drop of variability of Vickers hardness data and residual stress level qualitatively identify that the Fe–Ni–B coatings possess more consistent microstructure and mechanical integrity after the remelting process.     

Fabrication of Fe-Ti alloys by pulsed current-assisted reaction from iron, manganese and titanium oxide or titanium hydride

Fe-Ti alloys were prepared by applying a pulsed electric current through compacted mixtures of iron, manganese and titanium oxide (with carbon) or titanium hydride (without carbon). After ball milling the mixture into a fine powder, the mixture was heated up to 1373–1573 K in a carbon mold by applying a pulsed electric current, and the temperature was maintained for 3–10 min. When TiO₂ was used as a starting material, TiC was formed. Fe was alloyed into FeTi and Fe₂Ti, with Ti also observed. When the C content was lowered to 8.136 wt%, the remaining C content after pulsed current application decreased to 4.64 wt%. When using TiH₂ as a starting material, Fe was alloyed into FeTi and Fe₂Ti, and Ti, Mn, Fe, and FeMn₂ were also observed. For a Fe-Ti alloy prepared using titanium hydride as a starting material, hydrogen content vs. absorption time curves were obtained at various numbers of cycles and temperatures.     

Microstructure and oxidation behaviour of Ir-rich Ir–Al binary alloys

In the current study, alloys of Ir–11Al, Ir–23Al, Ir–30Al, Ir–41Al and Ir–45Al (at.%) were prepared to investigate the microstructure and oxidation behaviour of Ir-rich Ir–Al alloys. Ir(Al)_ss and/or β-IrAl intermetallic phases were found to exist in the prepared alloys. During isothermal oxidation at 1100 °C, the Ir(Al)_ss and β-IrAl individually changed to porous and dense Al₂O₃. The microstructure of the oxide scale formed on Ir–23Al was similar to that of its former alloy which possessed a dendrite-like configuration. It was found that the mass change of Ir–45Al followed a parabolic law, showing the best oxidation resistance among the Ir–Al alloys.     

Wear and thermal stability of TiCN-WC-Co-Cr3C2 cermets modified by TiN

This work assesses the suitability of TiCN-WC-Co-Cr₃C₂ cermet modified by TiN for cutting tool application. Three cermet compositions containing TiN with 5, 10 and 15 wt% were prepared by Spark Plasma Sintering (SPS). The prepared cermets were subjected to pin-on-disk wear testing using EN31 steel as a disc material. The wear testing was conducted at a constant load of 20 N with different sliding velocities: 0.23 m/s, 0.27 m/s, and 0.35 m/s, which corresponds to 150 rpm, 175 rpm, and 225 rpm respectively. The cermet composition 55TiCN-15WC-10Co-5Cr₃C₂–10TiN (all in wt%) has shown lowest mass loss during wear testing. The thermal stability of the cermets were assessed by conducting annealing studies on the prepared cermets at different temperatures: 600°, 800° and 1000 °C for a constant soaking time of 4 h. The prepared cermets had very good thermal stability up to 800 °C. Beyond this temperature, a drastic reduction in the hardness of the cermets was observed. Among the three cermet compositions, 60TiCN-15WC-10Co-5Cr₃C₂–10 TiN showed better thermal stability. The oxide phases formed in all the cermet compositions during annealing at high temperatures (1000 °C) retard their microstructures. As a result, the hardness was decreased.     

Crystal structure of novel hydrides in a Mg–Ni–H system prepared under an ultra high pressure

The crystal structure of novel hydrides in the Mg–Ni–H system has been studied using a powder X-ray diffraction and transmission electron microscopy. A cubic-anvil-type apparatus was utilized to prepare samples. The new hydride with a chemical composition of around MgH₂–60 at% Ni was synthesized at 1073 K for 2 h under a pressure as high as 5 GPa. From TGA analysis, the new hydride was found to be Mg₂Ni₃H_3.4. Orthorhombic and monoclinic crystal systems with a primitive cell were proposed as possible symmetries of the new hydride. X-ray and electron diffraction patterns of the new hydride were indexed in an orthorhombic structure with a=0.8859(4), b=1.3740(5), c=0.4694(2) nm. Moreover, decomposition of the hydride into Mg₂Ni was observed by the transmission electron microscopy.     

One-pot synthesis of highly stable silver nanoparticles-conducting polymer nanocomposite and its catalytic application

Herein, we report the preparation of highly stable Ag_nano–PEDOT nanocomposite by one-pot fashion in acidic condition using 3,4-ethylenedioxythiophene (EDOT) as a reductant and polystyrene sulfonate (PSS^?) as a dopant for PEDOT as well as particle stabilizer for silver nanoparticles (AgNPs). The above nanocomposite denoted as Ag_nano–PEDOT/PSS^? nanocomposite. The formation of AgNPs with concomitant EDOT oxidation was followed by UV–visible (UV–vis) spectroscopy at different time intervals. Ag_nano–PEDOT/PSS^? nanocomposite shows absorption bands at 380 and above 700 nm, which correspond to surface plasmon resonance (SPR) peak of AgNPs and oxidized PEDOT, respectively. Ag_nano–PEDOT/PSS^? nanocomposite was characterized by infrared (IR) spectroscopy, transmission electron microscopy (TEM), and XRD. TEM study reveals that AgNPs are distributed uniformly around PEDOT polymer with an average particle size diameter of 10–15 nm. In addition, Ag_nano–PEDOT/PSS^? nanocomposite was tested for the catalytic reduction of 4-nitrophenol. For comparing stability, we were also synthesized AgNPs in the absence of PSS^? (denoted as Ag_nano–PEDOT) using EDOT as reductant. UV–vis spectrum of Ag_nano–PEDOT nanocomposite revealed that AgNPs prepared in the absence of PSS^? was not stable.     

Effect of compression ratio on microstructure evolution of Mg–10%Al–1%Zn–1%Si alloy prepared by SIMA process

A new Mg–10%Al–1%Zn–1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation (SIMA) process. The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated. The results indicate that the average size of α-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%. In addition, the eutectic Mg₂Si phase in the Mg–10%Al–1%Zn–1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process. With the increasing of compression ratio, the morphology and average size of Mg₂Si phases do not change obviously. The morphology modification mechanism of Mg₂Si phase in Mg–10%Al–1%Zn– 1%Si alloy by SIMA process was also studied.     

Free-Cyanide Synthesis and Characterization of Cu–Zn Alloy by an Electrodeposition-Annealing Route

Substitution of cyanide in electroplating is a current challenge. We present an alternative method aiming to reduce the toxicity and the cost of electroplating of Cu–Zn alloy (usually prepared from cyanide baths) while maintaining the decorative qualities and anticorrosive properties of the coating. For this purpose, Cu–Zn alloys were obtained in two steps from non-cyanide electrolytes. First, a copper layer electrodeposited onto a nickel under-layer, followed by a thin layer of zinc from three different simple non-cyanide zinc baths. The Zn/Cu/Ni sandwich system was then subjected to heat treatment at a temperature of 400°C, to ensure the diffusion of zinc into the copper layer to give the desired Cu–Zn alloy structure. The synthesized films were characterized by using X-ray diffraction XRD, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). XRD demonstrated that the electrodeposited films are crystalline and present the Cu_0.7Zn_0.3 phase with preferential (111) orientation. An analysis of XRD patterns revealed that after heat treatment, the Cu–Zn alloys were composed of a predominating α-phase structure. The morphology and composition of the coatings depends on the zinc plating bath type. After annealing, well defined pseudospherical Cu–Zn grains were formed covering the entire substrate surface. The EDS analysis indicated the formation of Cu_0.7Zn_0.3 brass alloys. The results showed the feasibility of this low-cost new route for the preparation of good quality Cu–Zn alloys from cyanide-free electrolytes.     

X-ray absorption spectroscopy of iron-doped conducting polymers

X-ray absorption spectroscopy (XAS) measurements were performed at the Fe K edge to determine the iron local structure in chemically prepared polyaniline (PANI) and polypyrrole (PPy) samples prepared with FeCl₃ as an oxidant. The samples were conditioned at different pHs by an acid–base treatment. In both as synthesized-doped polymers, the observed dispersed Fe atoms were predominantly coordinated to chlorine as Fe(III)Cl_x species, where x=6 for PANI and x=4 for PPy samples suggesting that the polymer–counteranion bonding is weaker than the iron–chelate one. For the PANI samples submitted to basic treatment, three different sets of Fe distances were found: five Fe–O at 2.00 Å, three Fe–Fe at approximately 2.80 Å and five Fe–Fe at 3.00 Å and the near-edge spectra showed the presence of octahedrally coordinated Fe⁺³. These results strongly suggest the presence of small oxide/hydroxide aggregates. Similar data were obtained for PPy treated with NH₄OH.     

New developed quaternary refractory superalloys

The novel idea for designing quaternary superalloys by two kinds of binary alloys with coherent structure was applied to Ir–Nb–Ni–Al superalloys. Eight alloys were prepared by combining two sorts of binary alloys, Ir–Nb and Ni–Al, in different proportions. The effects of the mole fraction of Ir-based alloy or the L1₂ alloy on the microstructure and the 0.2% flow stress of quaternary alloys were investigated. Two sorts of coherent structure, fcc/L1₂–Ir₃Nb and fcc/L1₂–Ni₃Al, were observed in the quaternary superalloys. The new developed quaternary Ir-based superalloys are of the advantages of Ir-based alloys and Ni-based superalloys. The 0.2% flow stress of Ir–Nb–Ni–Al at 1200°C could reach up to 350 MPa and the compressive strains were improved greatly compared with Ir-based alloys.     

EPR studies of blends of polyaniline with poly(methyl methacrylate-co-glycidyl methacrylate iminodiacetic acid)

A novel conductive blends of polyaniline (PANI) with poly(methyl methacrylate-co-glycidyl methacrylate iminodiacetic acid) (PANI–PMGI) was prepared by in situ dispersion polymerization. The PANI–PMGI blends were characterized by UV–vis, FTIR and electron paramagnetic resonance (EPR) spectra. The structure of the PANI–PMGI blends was similar to emeraldine salt proved by UV–vis and FTIR. The value of ΔH_pp, lineshape, g factor, N_s and A/B ratio of blends were investigated by EPR. The results of EPR indicated that the intermolecular interaction between PANI and PMGI was dependent on the content of PANI and temperature.     

Mechanical and corrosion resistance properties of electrodeposited Cu–ZrO2 nanocomposites

Electrodeposited Cu–ZrO₂ nanocomposites were prepared by suspending ZrO₂ nanoparticles in an acid copper electroplating bath at pH ～1. The calculated average crystallite size of electrodeposited pure copper and Cu–ZrO₂ nanocomposites were ～32 and ～30?nm, respectively. The measured crystallite structure was fcc and the texture was (220) for both electrodeposited pure copper and Cu–ZrO₂ nanocomposites. The surface morphology and composition of electrodeposited pure copper and Cu–ZrO₂ nanocomposites were characterised by SEM with EDX analysis. The microhardness and wear resistance of the electrodeposited Cu–ZrO₂ nanocomposite was higher than that of pure copper. The corrosion resistances of electrodeposited Cu–ZrO₂ nanocomposite and pure copper were evaluated by electrochemical Tafel polarisation studies. This revealed that Cu–ZrO₂ nanocomposites have higher corrosion resistance than electrodeposited pure copper in 3.5% NaCl (w/v) solution.     

The Effect of Pre-oxidation Treatment on Corrosion Behavior of Ni–Cu–Fe–Al Anode in Molten CaCl<Subscript>2</Subscript> Salt

This article presents Ni–Cu–Fe–Al alloy as a novel inert anode used in FFC process (the Fray Farthing Chen) in molten calcium chloride salts for producing titanium. The alloy was prepared by vacuum induction melting; then utilized as anode material in molten CaCl₂ for 16 h at 900 °C. Morphology and the corrosion behavior of the samples were analyzed using scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The product on the cathode was analyzed using X-ray diffraction (XRD). After 16 h electrolysis of anodes, EDS and SEM analysis of the samples showed that the corrosion depth of the non-oxidized sample was shorter. Corrosion attacks more severe for the pre-oxidized sample than the non-oxidized sample, which indicated that the corrosion resistance of outer layer is higher on the non-oxidized sample. The XRD results show that the TiO₂ pellets were successfully reduced to the lower oxides using the Ni–Cu–Fe–Al inert anode.