Oxygen barrier properties of organic montmorillonite modified polyamide 11/Poly (vinyl alcohol) films

Organic montmorillonite (OMMT) nano‐platelets were exfoliated and well dispersed in fully bio‐based polyamide 11/Poly(vinyl alcohol) (PA11/PVA) blends. Significantly lower oxygen permeation rates (OTR) were detected for the PA11_72.5PVA_27.5OMMT_x films than those of PA11 and PA11_72.5PVA_27.5 films. An extremely low OTR of 0.218 cm³/m²·day·atm was found for PA11_72.5PVA_27.5OMMT₁ film modified with 1 PHR optimum concentration of well dispersed OMMT nano‐platelets. Similarly, the free volume characteristics evaluated for PA11_72.5PVA_27.5OMMT_x film series reduced to a minimum as the OMMT concentration reached the optimum value. As revealed by dynamic mechanical and differential scanning calorimetric analyses of PA11_72.5PVA_27.5OMMT_x film series, all dynamic glass transition temperature (T_g), melting temperature (T_m) and percentage crystallinity (W_c) values of PA11_72.5PVA_27.5OMMT_x films were noticeably higher than those of PA11_72.5PVA_27.5 film without addition of OMMT. In fact, T_gs, T_ms and W_cs evaluated for PA11_72.5PVA_27.5OMMT_x films increased to a maximum, as their OMMT reached the optimum concentration. The considerably enhanced oxygen barrier resistance found for PA11_72.5PVA_27.5OMMT_x films was ascribed to the considerably reduced free volume characteristics and much longer permeation path caused by impermeably OMMT nano‐platelets well dispersed in PA11_72.5PVA_27.5OMMT_x films.     

Moisture‐resistant and strength retention properties of supercritical CO2‐processed thermoplastic starch modified by polyvinyl alcohol with varying degrees of polymerization

The ease of melt‐processing, moisture‐resistance, and tensile retention properties of scCO₂ and polyvinyl alcohol (PVA)–modified thermoplastic starch (scCO₂TPS_xPVA^a_y) materials were explored in this investigation. These characteristics were considerably improved by PVA modification particularly with decreasing PVA degree of polymerization (DP). The intensities of O―H stretching bands of scCO₂TPS_xPVA^a_y were considerably larger, and peak location of O―H stretching bands were significantly smaller than those of the corresponding TPS_xPVA^a_y and reduced gradually with the decrease in PVA's DP. The ΔH of melting and diffraction peaks of V_h‐type crystals for conditioned TPS_xPVA^a_y and scCO₂TPS_xPVA^a_y were considerably smaller than those of corresponding TPS and TPS_xPVA^a_y aged for the same time period and gradually reduced in intensity with decreasing PVA's DP. Possible reasons accounting for the considerably improved melt processing, moisture resistance, tensile retention, and retrogradation of scCO₂TPS_xPVA^a_y with decreasing PVA's DP are proposed.     

PVA networks grafted with PDMS branches

We describe a simple and efficient synthesis of poly(vinyl alcohol) (PVA) networks fitted with polydimethylsiloxane (PDMS) branches (PVA_netw‐g‐PDMS). The syntheses were achieved in two steps: (1) Grafting by urethane linking PDMS carrying ? NCO termini (PDMS‐NCO) onto PVA fitted with a few (～4) photoreactive acryl amide groups (PVA_AA), followed by (2) Photocrosslinking the PVA_AA‐g‐PDMS to PVA_netw‐g‐PDMS. The use of the binary N‐methyl‐2‐pyrrolidone/tetrahydrofuran (NMP/THF, 67/33) solvent system enabled the thermodynamically unfavorable mixing of hydrophobic PDMS branches with hydrophilic PVA_AA backbones. The amphiphilic graft, PVA_AA‐g‐PDMS, was characterized by ¹H NMR spectroscopy, and the final graft network, PVA_netw‐g‐PDMS, by FTIR spectroscopy, DSC, and equilibrium swelling. The grafting of sufficient volumes of PDMS branches onto PVA_AA yields cocontinuous hydrophilic/hydrophobic PVA/PDMS domains, whose existence was demonstrated by swelling in both water and hexanes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5272–5277, 2009     

Regenerating Spent Solutions of Vanadium‐containing Heteropoly Acids in the Presence of Additives

Vanadium‐containing heteropoly acid solutions of Keggin H_3+xPMo_12–xV_xO₄₀ and modified H_aP_zMo_yV_xO_b types (P‐Mo‐V HPAs) are promising nanosized inorganic metal‐oxygen cluster compounds with the property of reversible oxidability (V^V ↔ V^IV). The oxidation of reduced P‐Mo‐V HPAs at a temperature of 130–170 °C and an oxygen pressure of 4 atm is a convenient method for their regeneration, but results in regeneration degree of only 75–88 %. Various materials with electron transfer or oxidative properties, such as nitrogen doped carbon nanofibers (N‐CNFs), Sibunit‐4, HNO₃, and MoO₂, were investigated as additives to facilitate and accelerate the regeneration of HPA solutions. Among the studied additives HNO₃ was found to show the best efficiency, resulting in regeneration degree of higher 95 %. Rapid and efficient regeneration of spent HPA catalysts is an important criterion for achieving high productivity and sustainability of oxidative processes on their basis.     

Site‐Specific Substitution Preferences in the Solid Solutions Li12Si7–xGex,Li12–yNaySi7, Na7LiSi8–zGez,and Li3NaSi6–vGev

The mixed silicide‐germanides Li₁₂Si_7–xGe_x, Na₇LiSi_8–zGe_z, and Li₃NaSi_6–vGe_v which could serve as potential precursors for Si_1–xGe_x materials were synthesized and characterized by X‐ray diffraction methods. The full solid solution series Li₁₂Si_7–xGe_x (0 ≤ x ≤ 7) is easily accessible from the elements and features preferential occupation of the more negatively charged crystallographic tetrel positions by Ge, which is the more electronegative element. In case of Na₇LiSi_8–zGe_z a broad solid solution range of 1.3 ≤ x ≤ 8 is available but the ternary silicide Na₇LiSi₈ could not be obtained by the tested methods of synthesis. The solubility of Ge in Li₃NaSi_6–vGe_v is highly limited to a maximum of v ≈ 0.5, and again the formally more negatively charged tetrel positions are preferred by Ge. Additionally, the two crystallographic Li positions in Li₁₂Si₇ with unusually large displacement parameters can be partially substituted by Na in Li_12–yNa_ySi₇ with 0 ≤ y ≤ 0.6. The statistical mixing of Li and Na in this solid solution contrasts the typical ordering of Li and Na in most ternary tetrelides.     

Preparation of cellulose nanofibers and their improvement on ultradrawing properties of ultrahigh molecular weight polyethylene nanocomposite fibers

Novel ultrahigh molecular weight polyethylene (UHMWPE)/cellulose nanofiber (CNF) (F₁₀₀CNF_y) and UHMWPE/modified cellulose nanofiber (MCNF^x) (F₁₀₀MCNF^x_y) as‐prepared nanocomposite fibers were successfully prepared by gel‐spinning F₁₀₀CNF_y and F₁₀₀MCNF^x_y gel solutions, respectively. CNF nanofillers with a specific surface area at 120 m²/g and a nanofiber diameter of 20 nm were successfully prepared by proper acid hydrolysis of cotton fibers using sulfuric acid solution. MCNF^x nanofillers were prepared by grafting various contents of maleic anhydride grafted polyethylene (PE_g‐MAH) onto CNF nanofillers. The ultimate σ_f value of the best‐prepared F₁₀₀MCNF^x_y drawn fiber reached 4.5 GPa, which is about 67% higher than that of the UHMWPE drawn fiber prepared without the addition of any nanofiller. To understand the interesting ultradrawing, orientation, and tensile properties of F₁₀₀CNF_y and F₁₀₀MCNF^x_y fibers, Fourier transform infrared, transmission electron microscopic analyses of the CNF and MCNF^x nanofillers, and scanning electron microscopic analyses of profile surfaces of the etched drawn fibers were performed. This is the first work in this area of research wherein very small amounts of MCNF^x nanofillers prepared from cotton fibers were efficiently used as nucleating agents to enhance the ultradrawing and ultimate tensile properties of F₁₀₀MCNF^x_y fibers. Copyright © 2016 John Wiley & Sons, Ltd.     

Reactivity Control of C?H Bond Activation over Vanadium–Silver Bimetallic Oxide Cluster Cations

Vanadium–silver bimetallic oxide cluster ions (V_xAg_yO_z⁺; x=1–4, y=1–4, z=3–11) are produced by laser ablation and reacted with ethane in a fast‐flow reactor. A reflectron time of flight (Re‐TOF) mass spectrometer is used to detect the cluster distribution before and after the reactions. Hydrogen atom abstraction (HAA) reactions are identified over VAgO₃⁺, V₂Ag₂O₆⁺, V₂Ag₄O₇⁺, V₃AgO₈⁺, V₃Ag₃O₉⁺, and V₄Ag₂O₁₁⁺ ions, in which the oxygen‐centered radicals terminally bonded on V atoms are active sites for the facile HAA reactions. DFT calculations are performed to study the structures, bonding, and reactivity. The reaction mechanisms of V₂Ag₂O₆⁺+C₂H₆ are also given. The doped Ag atoms with a valence state of +1 are highly dispersed at the periphery of the V_xAg_yO_z⁺ cluster ions. The reactivity can be well‐tuned gradually by controlling the number of Ag atoms. The steric protection due to the peripherally bonded Ag atoms greatly enhances the selectivity of the V–Ag bimetallic oxide clusters with respect to the corresponding pure vanadium oxide systems.     

The determination and assignment of a complete 14N quadrupole coupling tensor in liquid solution

¹⁴N line splittings in the spectrum of nitrobenzene (neat liquid) and metadinitrobenzene (dissolved in benzene), induced by an external electric field, have been used to determine the complete ¹⁴N quadrupole coupling tensor of these substances. Assuming that both molecules are rigid and planar, and that the quadrupole coupling tensors at the ¹⁴N nuclei are identical, the principal components in a local reference frame (x′, y′, z′) are (eQ/h)V_x′ x′ = ±0.34 MHz (eQ/h)V_y′_y′= ±1.18 Hz and (eQ/h)V_z′_z′ = ±1.52. The z′-direction is parallel to the CN bond and the y?direction is perpendicular to the plane of the nitrogroup. With these data the asymmetry parameter η = 0.55.     

Temperature and pressure dependence of the free volume in the perfluorinated polymer glass CYTOP: A positron lifetime and pressure‐volume‐temperature study

The microstructure of the free volume was studied for an amorphous perfluorinated polymer (T_g = 378 K). To this aim we employed pressure–volume–temperature experiments (PVT) and positron annihilation lifetime spectroscopy (PALS). Using the Simha‐Somcynsky equation of state the hole free volume fraction h and the specific free and occupied volumes, V_f = hV and V_occ = (1 ? h)V, were determined. Their expansivities and compressibilities were calculated from fits of the Tait equation to the volume data. It was found that in the glass V_occ has a particular high compressibility, while the compressibility of V_f is rather low, although h (300 K) = 0.108 is large. In the rubbery state the free volume dominates the total compressibility. From the PALS spectra the hole size distribution, its mean, 〈v_h〉, and mean dispersion, σ_h, were calculated. From a comparison of 〈v_h〉 with V_f a constant hole density of N_h′ = 0.25 × 10²¹ g^?1 was estimated. The volume of the smallest representative freely fluctuating subsystem, 〈V_SV〉 ∝ 1/σ_h², is unusually small. This was explained by an inherent topologic disorder of this polymer. 〈v_h〉 and σ_h show an exponential‐like decrease with increasing pressure P at 298 K. The hole density, calculated from N_h′ = V_f/〈v_h〉, seems to show an increase with P which is unexpected. This was explained by the compression of holes in the glass in two, rather than three, dimensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2519–2534, 2007     

Application of the inner product technique to double-well potentials in three-dimensional quantum systems by expanding the potential functions around their minima

Energy eigenvalues of double-well potentials for three-dimensional systems are calculated by means of an expansion of the potential function V(x,y,z;Z²,λ,a_IJ)=-Z²[x²+y²+z²] +λ{x⁴+y⁴+z⁴+2a_IJ[x²y²+x²z²+y²z²]} around its minimum, using the inner product technique, for various values of perturbation parameters Z²,λ and a_IJ. Some of the results calculated by this technique are compared with results obtained by other methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reaction of oligoalcohols with diepoxides: An easy,one‐pot way to star‐shaped,multibranched polymers. II. Poly(ethylene oxide) stars—synthesis and analysis by size exclusion chromatography triple‐detection method

An Erratum has been published for this article in Journal of Polymer Science Part A: Polymer Chemistry (2004) 42(10) 2575‐2576 Starlike, highly branched (A_xB_yA_z) macromolecules having from a few to 100 arms and molar masses up to 10⁵ were prepared in three stages with the one‐pot, arms‐core‐arms method (B_y stands for y molcules of former diepoxides introduced into the core). Oligoalcohols, at least partially converted into their alcoholate counterpart states, reacted with diepoxy compounds giving star‐shaped, highly branched macromolecules. With the properly chosen conditions, complete conversion of both starting components was achieved. In this article homostars built with the first and second generation of poly(ethylene oxide) arms (A_x and A_z, respectively) are described. The number of arms (f) was determined either by direct measurements of the number‐average molcular weight (M_n) of the first and second stars (M_n of arms A_x and A_z is known) or by calculating f from branching indices g and g′ determined from the radius of gyration and the limited viscosity number measured with size exclusion chromatography (SEC) triple detection with TriSEC software. For a few samples, M_n was measured with high‐speed membrane osmometry. The progress of the stars' formation was monitored by ¹H NMR, SEC, and matrix‐assisted laser desorption/ionization time‐of‐flight methods. Functionalization of the ? OH end groups in the second generation of arms was observed by ¹H and/or ³¹P NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1576–1598, 2004     

A model for transitional plane Couette flow

A simplified model of plane Couette flow is derived by means of a cross-stream (y) Galerkin expansion in terms of trigonometric functions appropriate for idealized stress-free boundary conditions at the plates. A set of partial differential equations is obtained, governing the in-plane (x–z) space-dependence of a velocity field taken in the form: u=U₀(x,z,t)+[1+U₁(x,z,t)]sin(πy/2), v=V₁(x,z,t)cos(πy/2), w=W₀(x,z,t)+W₁(x,z,t)sin(πy/2). Beyond Lorenz-like Waleffe's modeling (Waleffe 1997), this Swift–Hohenberg type of approach is expected to give an access to the microscopic mechanism of spatiotemporal intermittency typical of the transition to turbulence in plane Couette flow (Pomeau 1986, Bergé et al. 1998).     

Synthesis of new molybdenum-tungsten, vanadium-tungsten and vanadium-molybdenum-tungsten oxynitrides from freeze-dried precursors

Interstitial molybdenum-tungsten, vanadium-tungsten and vanadium-molybdenum-tungsten oxynitrides in the solid solution series Mo_1−zW_z(O_xN_y) and V_1−zW_z(O_xN_y) (z=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1), and V_1−u−zMo_uW_z(O_xN_y) (u, z=0.2, 0.33, 0.4, 0.6; u+z<1), have been obtained by ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the metal salts (NH₄VO₃, (NH₄)₆Mo₇O₂₄·4H₂O and (NH₄)₆W₁₂O₃₉·18H₂O). A study of the influence of the preparative variables on the outcomes of this procedure is presented. Compounds in the Mo_1−zW_z(O_xN_y) series are prepared as single phases by ammonolysis of the respective freeze-dried precursors (during 2 h) at different temperatures between 973 and 1023 K, optimised for each composition, followed by slow cooling of the samples (except for the Mo-only containing phase, in which fast cooling has been used). Compounds in the V_1−zW_z(O_xN_y) and V_1−u−zMo_uW_z(O_xN_y) series are prepared as single phases by ammonolysis (during 2 h) of crystalline precursors (as resulting from thermal treatment in air at 873 K, during 12 h, of the freeze-dried precursors) at 1073 K, followed by slow cooling of the samples. All the compounds in these series have the rock-salt crystal structure, in which the metal atoms are in an fcc arrangement, with non-metal atoms occupying octahedral interstitial positions. The materials have been characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy and magnetic measurements.     

Gas-Phase Synthesis of Singly and Multiply Charged Polyoxovanadate Anions Employing Electrospray Ionization and Collision Induced Dissociation

Electrospray ionization mass spectrometry (ESI-MS) combined with in-source fragmentation and tandem mass spectrometry (MS/MS) experiments were used to generate a wide range of singly and multiply charged vanadium oxide cluster anions including V_xO_y ^n– and V_xO_yCl^n– ions (x = 1–14, y = 2–36, n = 1–3), protonated clusters, and ligand-bound polyoxovanadate anions. The cluster anions were produced by electrospraying a solution of tetradecavanadate, V₁₄O₃₆Cl(L)₅ (L = Et₄N⁺, tetraethylammonium), in acetonitrile. Under mild source conditions, ESI-MS generates a distribution of doubly and triply charged V_xO_yCl^n– and V_xO_yCl(L)^(n–1)– clusters predominantly containing 14 vanadium atoms as well as their protonated analogs. Accurate mass measurement using a high-resolution LTQ/Orbitrap mass spectrometer (m/Δm = 60,000 at m/z 410) enabled unambiguous assignment of the elemental composition of the majority of peaks in the ESI-MS spectrum. In addition, high-sensitivity mass spectrometry allowed the charge state of the cluster ions to be assigned based on the separation of the major from the much less abundant minor isotope of vanadium. In-source fragmentation resulted in facile formation of smaller V_xO_yCl^(1–2)– and V_xO_y ^(1–2)– anions. Collision-induced dissociation (CID) experiments enabled systematic study of the gas-phase fragmentation pathways of the cluster anions originating from solution and from in-source CID. Surprisingly simple fragmentation patterns were obtained for all singly and doubly charged V_xO_yCl and V_xO_y species generated through multiple MS/MS experiments. In contrast, cluster anions originating directly from solution produced comparatively complex CID spectra. These results are consistent with the formation of more stable structures of V_xO_yCl and V_xO_y anions through low-energy CID. Furthermore, our results demonstrate that solution-phase synthesis of one precursor cluster anion combined with gas-phase CID is an efficient approach for the top-down synthesis of a wide range of singly and multiply charged gas-phase metal oxide cluster anions for subsequent investigations of structure and reactivity using mass spectrometry and ion spectroscopy techniques.      

Enhanced lithium electrochromism of atmospheric pressure plasma jet-synthesized tungsten/molybdenum oxide films for flexible electrochromic devices

Enhanced lithium electrochromic performances of mixed organo-tungsten oxide (W _x O _y C _z )/organo-molybdenum oxide (Mo _x O _y C _z ) films by a rapid codeposition onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at a short exposed duration of 23 s using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of hexacarbonyl precursors [W(CO)₆ and Mo(CO)₆] are investigated. The flexible organo-tungsten–molybdenum oxide (WMo _x O _y C _z ) films demonstrated noteworthy electrochromic performance for 200 cycles of reversible Li⁺ ion intercalation and deintercalation in a 1 M LiClO₄–propylene carbonate electrolyte by the switching measurements of potential sweep from ?1 to 1 V at a scan rate of 50 mV/s and the potential step at ?1 and 1 V, even after being bent 360^o around a 2.5-cm diameter rod for 1,000 cycles. The optical modulation (ΔT) of 61.3 % for MoO _y C _z films at a wavelength of 795.6 nm was significantly improved up to 72.5 % for WMo _x O _y C _z films cosynthesized with an APPJ.     

Strukturuntersuchungen an Usoviten: Ba2CaMIIV2F14 (MIII = Mn,Fe), Ba2CaMnFe2F14 und Ba2CaCuM2IIIF14 (MIII = Mn,Fe, Ga)

Structural Studies with Usovites: Ba₂CaM^IIV₂F₁₄ (M^III = Mn, Fe), Ba₂CaMnFe₂F₁₄ and Ba₂CaCuM₂^IIIF₁₄ (M^III = Mn, Fe, Ga). Single crystals of six compounds Ba₂CaM^IIM₂^IIIF₁₄ were prepared to refine their usovite type structure (space group C2/c, Z = 4) using X‐ray diffractometer data. The cell parameters of the phases studied with M^IIM₂^III= MnV₂, FeV₂, CuMn₂, MnFe₂, CuFe₂ und CuGa₂ are within the range 1374≤a/pm≤1384, 534≤b/pm≤542, 1474≤c/pm≤1510, 91, 3≤ß/°≤93, 2. The atoms Ca and M^II are incompletely ordered on the 8‐ and 6‐coordinated positions, 4e and 4b, respectively. In the case of Ba₂CaFeV₂F₁₄ and Ba₂CaCuGa₂F₁₄ there is reciprocal substitution (x≈0, 1): (Ca_1‐xM_x^II) (4e) and (M_1‐x^IICa_x) (4b). In the case of the other usovites Ca‐enriched phases Ba₂Ca(M_1‐y^IICa_y)M₂^IIIF₁₄ occured (up to y≈0, 35), exhibiting partial substitution at the octahedral position (4b) only, showing a corresponding increase in M^II‐F distances. The distortion of [M^IIF₆] and [M^IIIF₆] octahedra within the structure is considerably enhanced on replacement by Cu^II and Mn^III. The results of powder magnetic susceptibility measurements of Ba₂CaMnV₂F₁₄ and Ba₂CaFeV₂F₁₄ (T_N≈7K) are reported.     

Synthesis and Structure of the new Fluoride Bromide Ba6.668(2)Ca0.332(2)F12Br2 and Solid Solutions with Composition Ba7−xCaxF12(ClyBr1−y)2 with x = ∼0.5, 0 < y < 1

Crystals of the chemical composition Ba₇F₁₂Cl₂ were modified by adding a small amount of Ca²⁺ to allow the synthesis of the corresponding bromine compound Ba^[Ca]₇F₁₂Br₂. These samples were prepared in a NaBr flux and characterized by single crystal x‐ray diffraction. The new structure crystallizes in a disordered arrangement in the hexagonal space group P6₃/m (176). The calcium ion has a coordination number of 6. Solid solutions on the heavy halide position can be synthesised in a NaCl/NaBr flux to obtain the compounds Ba_7?xCa_xF₁₂(Cl_yBr_1?y)₂ with x = ～0.5 and 0 < y < 1. Regardless the amount of calcium used in the preparation process, the Ca stoichiometry in the compound is always between 0.3 and 0.5. The lattice parameters differ depending on the Ca‐ and Br‐content between 1053.81(5) ? a = b ? 1058.93(3) pm and 421.21 ? c ? 426.78(3) pm.     

Structural Interconversion of Bimetallic Carbonyl Clusters ­Induced by a NHC Ligand and Its Selectivity on Fragments

The reactions of IMes‐HCl with bimetallic iron‐copper clusters were investigated and it showed that interconversions among bimetallic Fe_xCu_y(CO)_z^n– clusters were induced by IMes‐HCl. The reaction priority of IMes‐HCl with fragments in Fe_xCu_y(CO)_z^n– was also investigated and the reaction behaviors of zero valent Fe(CO)₄ and divalent Fe(CO)₄ with IMes‐HCl were discussed.     

Molecular Layer Deposition and Thermal Transformations of Titanium(Aluminum)-Vanadium Hybrid Organic-Inorganic Films

In this work Molecular layer deposition (MLD) technique used to synthesize titanium-vanadium (TiV _x C _y O _z ) and aluminum-vanadium (AlV _x C _y O _z ) hybrid organic-inorganic films via alternating surface reactions of titanium tetrachloride (or trimethylaluminum), vanadium oxochloride, and ethylene glycol. Using in situ monitoring it was found that the surface reactions were self-limiting at temperatures of 90 and 115°C. The coating thickness per molecular layer deposition cycle (growth rate) at 115°C on a silicon substrate varied from 5.8 to 11.4 Å/cycle, and the film densities, from 1.7 to 2.0 g cm^–3. An analysis of the samples obtained at 115°C revealed their amorphous structure. A thermal treatment of titanium-vanadium films at 450°C in air resulted in formation of highly structured coatings. These coatings were composed of nanowires of single-crystal vanadium oxide (V₂O₅) and mixed nanostructures of titanium and vanadium oxides. Increase in thermal treatment temperature to 500°C resulted in elongation of the V₂O₅ nanowires up to tens of micrometers and in their separation from the substrate. A thermal treatment of aluminum-vanadium films in air resulted in formation of a low-density film. Pyrolysis of the films in an inert gas yielded composite coatings containing domains of graphitized carbon. These films can be potentially useful in modern devices for energy storage, electronics, medicine and other promising fields of technology.     

Hydrolytic precipitation of magnesium polyvanadates in vanadium (IV, V) solutions

The phase and chemical composition of precipitates formed in Mg(VO₃)₂-VOSO4-H₂O system at initial pH from 1 to 7 and temperature from 80 to 90°C was studied. Polyvanadates of variable composition Mg _x V _y ⁴⁺V_12-y ⁵⁺¹O_31–δ · nH₂O (0.7 ≤ x ≤ 1.3, 1.2 ≤ y ≤ 2.4, 0.7 ≤ δ = 1.4) were formed at pH from 1 to 4 and V⁴⁺/V⁵⁺ ratio from 0.43 to 9. Compounds with the general formula Mg _x V _y ⁴⁺V_6-y ⁵⁺O_16-δ · nH₂O (0.7 ≤ x ≤ 0.65, y = 1.0, 0.8 ≤ δ ≤ 0.85) were formed at pH from 6.0 to 7.0 and V⁴⁺/V⁵⁺ ratios from 0.11 to 0.25. The maximum V⁴⁺ concentration (y = 2.4) in the precipitates was achieved at the VV⁴⁺/V⁵⁺ solution ratio of 1.0 and pH = 3. The precipitates in solutions with pH 3 were formed only upon addition of VO²⁺ ions with the maximum rate at a V⁴⁺/V⁵⁺ ratio of 0.33. These processes were limited by second-order reactions on the surface of polyvanadates.