Synthesis, infrared stealth and corrosion resistance of organically modified silicate-polyaniline/carbon black hybrid coatings

Hybrid coatings based on organically modified silicate-polyaniline/carbon black (Ormosil-PANI/CB) were synthesized through a sol-gel technique with different carbon black (10-30 wt%) and PANI/CB (10-30 wt%) contents. These hybrid films were deposited via spin coating onto an aluminum alloy in order to improve the corrosion protection and to act as infrared stealth coatings. The effects induced by the PANI/CB composites on the chain dynamic, thermal properties, infrared stealth, and anticorrosion performances of the coated samples were investigated. The rotating-frame spin-lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly cross-linked and dense. Thermal properties of these Ormosil-PANI/CB hybrids have been improved over the pure Ormosil analyzed by thermal gravimetric analysis (TGA). The thermal extinction of the hybrid coatings increased with the increase in the carbon black and PANI/CB content. Potentio-dynamic and salt-spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates.     

Characterization of chromate conversion coating on AA7075‐T6 aluminum alloy

Chromate conversion coatings (CCCs) on AA7075‐T6 were characterized using scanning electron microscopy, focused ion beam sectioning and scanning transmission electron microscopy with nano‐electron dispersive spectroscopy line profiling. The thickness and composition of the CCC was different at different locations on the heterogeneous microstructure of AA7075‐T6. The coating formed on the matrix phase was much thicker than that formed on the coarse Al–Cu–Mg, Al–Fe–Cu and Mg–Si intermetallic particles. Nano‐electron dispersive spectroscopy line profiling indicated that the coating on the Al–Fe–Cu particles was similar to the CCC formed on the phase matrix, primarily a chromium oxide. However, the coatings on the Al–Cu–Mg and Mg–Si particles were mixed Al/Mg/Cr oxide and Mg oxide, respectively. The growth of CCC followed a linear‐logarithmic kinetic rate law. The observations of this study support the sol‐gel model of CCC formation. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparing the Atomic Structures of Binary MO2-SiO2 (M = Ti, Zr or Hf) Xerogels

The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO₂-SiO₂ and HfO₂-SiO₂ materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO₂) _x (SiO₂)_{1 – x} (M = Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750°C. Detailed observations for TiO₂-SiO₂ and ZrO₂-SiO₂ xerogels provide a basis for interpretation of new results for HfO₂-SiO₂ xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO₂, but remain very finely mixed with silica network for ZrO₂ and HfO₂.     

Electropolymerized coatings of poly(o‐anisidine) and poly(o‐anisidine)‐TiO2 nanocomposite on aluminum alloy 3004 by using the galvanostatic method and their corrosion protection performance

Poly(o‐anisidine) (POA) and poly(o‐anisidine)‐TiO₂ (POA‐TiO₂) nanocomposite coatings on aluminum alloy 3004 (AA3004) have been investigated by using the galvanostatic method. The electrosynthesized coatings were characterized by FT ‐ IR spectroscopy, XRD, SEM ‐ EDX and SEM. The corrosion protection performance of POA and POA‐TiO₂ nanocomposite coatings was investigated in the 3.5% NaCl solution by using potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results show that the corrosion rate of the nanocomposite coatings is about 900 times lower than the bare AA3004 under optimal conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of SiC/nano‐CeO2 on wear resistance and microstructures of Ti3Al/γ‐Ni matrix laser‐cladded composite coating on Ti–6Al–4V alloy

The Ti–6Al–4V alloy is an important aviation material, but has a poor resistance to slide wear. Laser cladding of the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ + SiC/nano‐CeO₂ preplaced powders on the Ti–6Al–4V alloy can form the Ti₃Al/γ‐Ni matrix composite coating, which improves the wear resistance of the substrate. In this study, the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ + SiC/nano‐CeO₂ laser‐cladded coating was researched by means of X‐ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The experimental results indicate that under the action of SiC/nano‐CeO₂, this composite coating exhibited a fine microstructure. Furthermore, the proper content of nano‐CeO₂ decreased the crack tendency. The results above indicated that, it is feasible to improve the tribological property of the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ laser‐cladded coating by adding of SiC/nano‐CeO₂. Copyright © 2011 John Wiley & Sons, Ltd.     

An Anti CuO2‐type Metal Hydride Square Net Structure in Ln2M2As2Hx (Ln=La or Sm,M=Ti,V, Cr,or Mn)

Using a high pressure technique and the strong donating nature of H⁻, a new series of tetragonal La₂Fe₂Se₂O₃‐type layered mixed‐anion arsenides, Ln₂M₂As₂H_x, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M₂H square net, which has anti CuO₂ square net structures accompanying two As³⁻ ions, is sandwiched by (LaH)₂ fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La₂Ti₂As₂H_2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters.     

Reactions of rac‐(ebthi)M(η2‐Me3SiC2SiMe3) (M=Ti,Zr) with Aryl Nitriles

The reactions of the Group 4 metallocene alkyne complexes rac‐(ebthi)M(η²‐Me₃SiC₂SiMe₃) ( 1 a : M=Ti, 1 b : M=Zr; rac‐(ebthi)=rac‐1,2‐ethylene‐1,1′‐bis(η⁵‐tetrahydroindenyl)) with Ph?C?N were investigated. For 1 a , an unusual nitrile–nitrile coupling to 1‐titana‐2,5‐diazacyclopenta‐2,4‐diene ( 2 ) at ambient temperature was observed. At higher temperature, the C?C coupling of two nitriles resulted in the formation of a dinuclear complex with a four‐membered diimine bridge ( 3 ). The reaction of 1 b with Ph?C?N afforded dinuclear compound 4 and 2,4,6‐triphenyltriazine. Additionally, the reactivity of 1 b towards other nitriles was investigated.     

An Anti CuO2‐type Metal Hydride Square Net Structure in Ln2M2As2Hx (Ln=La or Sm,M=Ti,V, Cr,or Mn)

Using a high pressure technique and the strong donating nature of H^?, a new series of tetragonal La₂Fe₂Se₂O₃‐type layered mixed‐anion arsenides, Ln₂M₂As₂H_x, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M₂H square net, which has anti CuO₂ square net structures accompanying two As^3? ions, is sandwiched by (LaH)₂ fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La₂Ti₂As₂H_2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters.     

Bildung und Charakterisierung von Oberflächenverbindungen in den Systemen (C6H5CH2)4M/γ-Al2O3 (M = Ti,Zr)

Formation and Characterization of Surface Compounds in the Systems (C₆H₅CH₂)₄M/γ-Al₂O₅ (M = Ti, Zr) By O-bridges anchored surface-compounds are formed by protolytic splitting off of benzyl groups if tetrabenzyltitanium and -zirconium are added to γ-alumina. These compounds contain the metal in different oxidation states in dependence on the carrier/substrate ratio and the density of OH groups on the alumina surface. The different kinds of surface compounds are discussed. Furthermore, the products formed by thermal decomposition and hydrogenolysis of the surface compounds were analysed. With regard to catalytic conversion reactions of hydrocarbons systems of the type (C₆H₅CH₂)₄M/Pt/γ-Al₂O₃were involved in the investigations.     

Syntheses and Structures of New Trinuclear MIILnMII (M = Ni,Co; Ln = Gd,Ce) Complexes with 2, 6‐Bis(acetobenzoyl)pyridine

One‐pot reactions of 2, 6‐bis(acetobenzoyl)pyridine (H₂L) with a mixture of LnCl₃ (Ln = Ce, Gd) and Ni(CH₃COO)₂ (ratio 2:1:2) in CH₂Cl₂/MeOH in the presence of a supporting base like Et₃N give trinuclear complexes with the general composition [Ni₂Ln(L)₂(CH₃COO)₃(MeOH)_2/3] ( 1 ) in high yields. Trinuclear [Ni₂Ln(L)₂(PhCOO)₃(MeOH)₂] ( 2 ) complexes are formed when similar reactions are performed starting from NiCl₂, and benzoic acid (PhCOOH) is added subsequently. Under the same conditions, reactions with the corresponding cobalt(II) salts result in the formation of a neutral [Co₈(μ₃‐O)₂(L)₆] complex, which has a bis(triple‐helical) structure. The cobalt(II) analogues to compounds 1 and 2 , however, can be synthesized by a pre‐treatment of the lanthanide salts with H₂L and subsequent addition of the cobalt salts, and benzoic acid (in the case of 2 ).     

Synthesis and Characterization of the Monomeric Sterically Encumbered Diaryls E{C6H3‐2,6‐(C6H3‐2,6‐Pri2)2}2 (E = Ge,Sn, or Pb)

The reaction of two equivalents of LiC₆H₃‐2,6‐(C₆H₃‐2,6‐Prⁱ₂)₂ with GeCl₂·dioxane, SnCl₂ or PbBr₂ in a diethyl ether solution resulted in the isolation of the monomeric σ‐bonded diaryl tetrylene series E{C₆H₃‐2,6‐(C₆H₃‐2,6‐Prⁱ₂)₂}₂ (E = Ge ( 1 ), Sn ( 2 ), or Pb( 3 )). Compounds 1 ‐ 3 are highly sterically congested blue crystalline solids, which possess V‐shaped structures and wide interligand bond angles. The solid state structures of 1 ‐ 3 were determined by single‐crystal X‐ray methods while their solution structures were investigated by UV spectroscopy and in the cases of 2 and 3 , respectively, by ¹¹⁹Sn and ²⁰⁷Pb NMR spectroscopy. The series 1 ‐ 3 constitutes the most sterically crowded examples of σ‐bonded diorgano group 14 derivatives yet isolated and, in contrast to previously reported: ER₂ species, the C‐E‐C angles increase with increasing atomic number.     

Preparation,Crystallographic, Spectroscopic and Magnetic Characterization of Low‐Valency Nitridometalates Li2[(Li1‐xMx)N] with M = Cu,Ni

Thermogravimetric and difference thermal analyses show that the reactions of lithium nitride with the transition metals Cu and Ni under molecular nitrogen to form phases Li₂[(Li_1‐xM^I_x)N] take place above 673 K. The maximum weight gains are reached at 926 K and 968 K for M = Cu and Ni, respectively. At higher temperatures, the ternary phases Li₂[(Li_1‐xM^I_x)N] decompose, limiting the substitutional level x. In the temperature range of 773 K — 873 K, the successful synthesis of Li₂[(Li_1‐xNi^I_x)N] (0 < x ≤ 0.85(1)) single phase products is demonstrated. Maximum substitution obtained for the Cu phases is x_max= 0.43(1). The dependence of the lattice parameters of the hexagonal unit cell on x is almost linear. The magnetic moment of M strongly depends on x. At low x the magnetic moments in phases with M = Ni are presumably enhanced by orbital effects. A decrease of μ_eff with x to μ_eff(x = 1) → 0 is explained by delocalization of the magnetic moments and by the gradual formation of a metal for the hypothetical compound Li₂[NiN] (x = 1). XAS spectroscopy at the transition metal K‐edges shows that Cu and Ni principally correspond to d¹⁰‐ and d⁹‐configurations, respectively.     

Crystal structures and magnetic properties of 6H-perovskite-type oxides Ba3MIr2O9 (M=Mg, Ca, Sc, Ti, Zn, Sr, Zr, Cd and In)

Crystal structures and magnetic properties of quaternary oxides Ba₃MIr₂O₉ (M=Mg, Ca, Sc, Ti, Zn, Sr, Zr, Cd and In) were investigated. Rietveld analyses of their X-ray diffraction data indicate that they adopt the 6H-perovskite-type structure with space group P6₃/mmc or, in the case of M=Ca, Sr and Cd, a monoclinically distorted structure with space group C2/c. The Ir valence configurations are (M=Mg, Ca, Zn, Sr and Cd), (M=Sc and In) and (M=Ti and Zr). Magnetic susceptibility and specific heat measurements were carried out. In the , the Ir⁵⁺ ions have a non-magnetic ground state and the magnetic behavior for these compounds is explained by the Kotani's theory. For , the effective magnetic moment of these compounds is significantly small, although the Ir⁴⁺ ions have magnetic moment, which indicates the existence of the strong antiferromagnetic interaction between Ir⁴⁺ ions in the Ir⁴⁺₂O₉ face-shared bioctahedra. In the case of , a specific heat anomaly was found at about 10 K (M=Sc) and 1.6 K (M=In), which suggests the magnetic ordering of the magnetic moments of Ir⁴⁺ in the (Ir⁴⁺Ir⁵⁺)O₉ bioctahedra.     

M(benzo‐18‐crown‐6)I4 (M = Cd,Hg): Tetraiodide,Iodide–Iodine Adduct,or an Inclusion Compound of Iodine in MI2@(benzo‐18‐crown‐6)?

M(benzo‐18‐crown‐6)I₄ (M = Cd, Hg) are obtained as red columnar crystals from the reactions of benzo‐18‐crown‐6 (b18c6), cadmium and mercury iodide, respectively, and iodine in molar ratios of 1:1:2 in acetonitrile. They both crystallize with the orthorhombic crystal system, P2₁2₁2₁, a = 833.7(1), b = 1610.9(1), c = 1846.8(1) pm, V = 2480.3(1) 10⁶·pm³, Z = 4, for M = Cd and a = 823.4(1), b = 1616.5(1), c = 1866.1(1) pm, V = 2483.8(2) 10⁶·pm³ for M = Hg. The crystal structures consist of [M(b18c6)]I₂ molecules which are connected to a slightly lengthened iodine molecule via a secondary contact, according to the formulation I₂@[MI₂@(b18c6)].     

Syntheses and Characterization of Cyanide‐Bridged Bimetallic Compounds Zn(terpy)(H2O)M(CN)4 (terpy = 2,2′:6′,2′′‐ter­pyridine; M = Ni,Pd, Pt) with Linear Chains

The self‐assembly reaction of zinc ions with tetracyanometalates in the presence of the tridentate chelated ligand 2,2′:6′,2′′‐terpyridine (terpy) yielded three cyanide‐bridged bimetallic compounds of general formula Zn(terpy)(H₂O)M(CN)₄ [M = Ni ( 1 ), Pd ( 2 ), Pt ( 3 )]. Compounds 1 – 3 were characterized by X‐ray diffraction (XRD), infrared spectroscopy (IR), and thermogravimetric (TG) analysis. Single‐crystal XRD analysis revealed that compounds 1 – 3 are isostructural and the structure consists of [Zn(terpy)(H₂O)]²⁺ moieties and [M(CN)₄]^2– units linked alternatively to generate a one‐dimensional (1D) linear chain. The chains are further connected together through hydrogen bonding and π–π stacking interactions, forming a 3D supramolecular network. IR spectroscopic analysis indicated the presence of cyanide groups and terpy ligands in the structure. TG and powder XRD results showed that compounds 1 – 3 have higher thermal stabilities and exhibited irreversible for desorption/resorption of one coordinated water molecule.