Crystal structure of new compound (Rb,K)<Subscript>2</Subscript>Cu<Subscript>3</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>2</Subscript>

A new compound of (Rb,K)₂Cu₃(P₂O₇)₂ is obtained by high-temperature reactions from a mixture of RbNO₃, KNO₃, Cu(NO₃)₂, and (NH₄)₄P₂O₇. The crystal structure was solved by direct methods and refined to R ₁ = 0.056 for 5022 independent reflections. The compound belongs to a rhombic crystal system, P2₁2₁2₁, Z = 8, a = 9.9410(7) Å, b = 13.4754(6) Å, c = 18.6353 (3) Å, and R = 0.056. The basis of the structure is a complex copper-phosphate skeleton of the composition of [Cu₃(P₂O₇)₂]^2–, which can be regarded as consisting of two types of heteropolyhedral layers parallel to the (001) plane. The layers are alternated with each other, forming a frame, in the cavities of which the positions of alkali cations are located, statistically populated with K⁺ and Rb⁺ ions. Based on the refined populations of the positions of alkali cations, an exact chemical formula of the compound can be written as Rb_1.28K_0.72Cu₃(P₂O₇)₂. The compound is the most complex among those known to this day of the composition of A₂ ^IB₃ ^II(P₂O₇)₂ (A = Li, Na, K, Rb, or Cs; B = Ni, Cu, or Zn).     

Photoreduction of CO<Subscript>2</Subscript> into CH<Subscript>4</Subscript> using Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> double-layered dense films

Nano-sized bismuth sulfide (Bi₂S₃) and titanium dioxide (TiO₂) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO₂) to methane (CH₄). Four double-layered dense films were fabricated with different coating sequences—TiO₂ (bottom layer)/Bi₂S₃ (top layer), Bi₂S₃/TiO₂, TiO₂/Bi₂S₃: TiO₂ (1 : 1) mix, and Bi₂S₃: TiO₂ (1 : 1) mix/Bi₂S₃: TiO₂ (1 : 1) mix—and applied to the photoreduction of CO₂ to CH₄; the catalytic activity of the fabricated films was compared to that of the pure TiO₂/TiO₂ and Bi₂S₃/Bi₂S₃ doubled-layered films. The TiO₂/Bi₂S₃ double-layered film exhibited superior photocatalytic behavior, and higher CH₄ production was obtained with the TiO₂/Bi₂S₃ double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO₂/Bi₂S₃ double-layered film was proposed, and it was attributed in effective charge separation.     

Corrosion protection of AA6061 T6-10 % Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite by molybdate conversion coatings

The corrosion protection performance of aluminum composite materials was investigated in 3.5% NaCl solution for time ranging between 1–60 days. Series of specimens were treated in molybdate solutions under different conditions. Free immersion and electrochemical activation techniques were used to apply the molybdate layer. The specimens which were directly treated or pickled before molybdate treatment showed severe pitting corrosion. Conversely, the specimens which were subjected to an oxide thickening step before the molybdate treatment showed outstanding corrosion protection. XPS revealed a higher amount of molybdate as MoO₄^2– for the specimens prepared by electrochemical activation technique than for the free immersion technique.     

Combustion and structure formation in the Ti-Ta-C-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> system

Biocompatible composites (Ti, Ta)C _x + Ca₃(PO₄)₂ for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca₃(PO₄)₂ mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have little or no influence on the burning velocity U and combustion temperature T _c. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.      

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript>-OSO<Subscript>3</Subscript>H: an efficient hierarchical nanocatalyst for the organic quinazolines syntheses

A sulfonic acid functionalized titanium dioxide quasi-superparamagnetic nanocatalyst Fe₃O₄@SiO₂@TiO₂-OSO₃H with average size of 61 nm and semispherical shape with surface area about 97 m² g^?1 with saturation magnetization 17.7 emu g^?1 and the coercivity 9.84 Oe was successfully synthesized. The structure and morphology of the nanocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy, X-ray diffraction pattern, transmission electron microscopy, field-emission scanning electron microscopy, vibrating sample magnetometer and Brunauer–Emmett–Teller surface area analysis. The catalytic usage of the nanocatalyst was exemplified in synthesis of 2,3-dihydroquinazolin-4(1H)-one and spiroquinazolin-4(3H)-one derivatives in deep eutectic solvents (DESs) based on choline chloride and urea. We suggest that the synergistic effects in catalytic activities of titanium dioxide, organic acid and the CO₂ capture property of DES are the main reasons for the improvement of catalytic activity. The synthesized spiroquinazolinones and dihydroquinazolinones derivatives were characterized by FT-IR, ¹H and ¹³C nuclear magnetic resonance spectroscopy. The magnetic nanocatalyst exhibit high catalytic activity and can be simply separated from reaction media by an external magnet in a few seconds and could be reused for six cycles without significant loos in activity, which indicates the good immobilization of sulfonic acid on the magnetic titanium dioxide support. Furthermore, the solvent which has been used in this work can be readily isolated and reused for several times.     

Low-temperature fabrication of TiO<Subscript>2</Subscript> film on flexible substrate by atmospheric roll-to-roll CVD

Titanium dioxide (TiO₂) thin film was fabricated using titanium isopropoxide as a precursor through an atmospheric low-temperature roll-to-roll chemical vapor deposition method. TiO₂ was deposited on the PET substrate in the temperature range of room temperature to 100°C, and the working pressure was 740 Torr. The surface morphology of TiO₂ thin film was analyzed by field emission scanning electron microscopy and a 2D surface profiler. The results revealed that the growth rate of TiO₂ film was 31 nm/min at 100°C, and it also showed that the surface is uniform and smooth. Moreover, the lowest root mean square roughness (R _q) value of 1.87 nm was obtained for TiO₂ film prepared at 100°C. The composition of TiO₂ film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The film showed very good chemical and optical properties while increasing the substrate deposition temperature. The UV–Vis spectroscopy analysis revealed that TiO₂ films exhibited excellent optical transmittance, more than 91% observed in the visible region.     

Preparation and Characterization of Mesoporous MoO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> Composite with High Surface Area by Self-Supporting and Ammonia Method

Abstract  

A mesoporous MoO₃/TiO₂ composite was prepared from titanate derivative by consecutive self-supporting and ammonia method. All samples were characterized by X-ray Diffraction, N₂ adsorption–desorption, Raman Spectra and Field-Emission Scanning Electron Microscopy. The results showed that mesoporous MoO₃/TiO₂ composite had a higher surface area (173 m²/g) and a better MoO₃ dispersion than that prepared by traditional impregnation (90 m²/g). As for hydrodesulfurization tests, mesoporous MoO₃/TiO₂ composite in this case presented a better catalytic performance, attributed to its high surface area and good dispersion of MoO₃. It can be found that self-supporting played a key role in preparing mesoporous MoO₃/TiO₂ composite with high surface area. Additionally, aqueous ammonia could effectively dissolve excess MoO₃, which helped to obtain mesoporous MoO₃/TiO₂ composite with better dispersion of MoO₃.     

Combustion synthesis of some compounds in the Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system

At least four compounds, viz. LiAlO₂, LiAl₅O₈, Li₅AlO₄ and Li₂Al₄O₇, are known in the Li₂O-Al₂O₃ system. These compounds are important for several technological applications. Combustion synthesis of these compounds using urea as a fuel was attempted. LiAlO₂ and LiAl₅O₈ could be successfully prepared by choosing the starting materials in required stoichiometric ratios. Li₂Al₄O₇ was not obtained as a pure phase; γ-LiAlO₂ was formed as an impurity phase. Li₅AlO₄ could not be prepared by combustion process. Some phosphors based on these aluminates could also be prepared. Activation of these aluminates with Fe³⁺, Mn⁴⁺, Cu⁺, etc. was successfully achieved. Excitation and emission spectra for LiAl₅O₈: Fe³⁺, LiAl₅O₈: Mn²⁺, and Li₂Al₄O₇: Cu⁺ are reported.     

Preparation of hydrophobic SiO<Subscript>2</Subscript>@(TiO<Subscript>2</Subscript>/MoS<Subscript>2</Subscript>) composite film and its self-cleaning properties

TiO₂/MoS₂ composite was encapsulated by hydrophobic SiO₂ nanoparticles using a sol–gel hydrothermal method with methyltriethoxysilane (MTES), titanium tetrachloride (TiCl₄), and molybdenum disulfide (MoS₂) as raw materials. Then, a novel dual functional composite film with hydrophobicity and photocatalytic activity was fabricated on a glass substrates via the combination of polydimethylsiloxane adhesives and hydrophobic SiO₂@(TiO₂/MoS₂) composite particles. The influence of the mole ratios of MTES to TiO₂/MoS₂ (M:T) on the wettability and photocatalytic activity of the composite film was discussed. The surface morphology, chemical compositions, and hydrophobicity of the composite film on the glass substrate were investigated by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle (water CA) measurements. The results indicated that the composite film exhibited stable superhydrophobicity and excellent photocatalytic activity for degradation of methyl orange (MO) even after five continuous cycles of photocatalytic reaction when M/T was 7:1. The water CA and degradation efficiency for MO remained at 154° and 94%, respectively. Further, the composite film showed a good non-sticking characteristic with the water sliding angle (SA) at about 4°. The SiO₂@(TiO₂/MoS₂) composite consisting of hydrophobic SiO₂ nanoparticles and TiO₂/MoS₂ heterostructure could provide synergistic effects for maintaining long-term self-cleaning performance.     

A Visible‐Light‐Driven Photocatalyst of NASICON Li2Ni2(MoO4)3 Nanoparticles

A visible‐light‐driven photocatalyst based on the well‐known cathode material of NASICON‐type Li₂Ni₂(MoO₄)₃ was prepared by a modified Pechini method. The sample was characterized by X‐ray diffraction, scanning electron microscope, transmission electron microscopy, and UV‐vis absorption spectrum. The average size of Li₂Ni₂(MoO₄)₃ particle is below 50 nm. NASICON nanoparticles Li₂Ni₂(MoO₄)₃ has an efficient absorption in the UV‐visible light wavelength region with a direct allowed electronic transition of 2.07 eV. The photocatalytic properties of Li₂Ni₂(MoO₄)₃ were evaluated by the photodegradation of methylene blue (MB). Li₂Ni₂(MoO₄)₃ has an efficient photocatalytic activity and could be a potential photocatalyst driven by visible‐light. The photocatalytic activity was discussed on the optical absorption and special hexagonal tunnel structure connected by optical active centers of MoO₄ and NiO₆ and its good conductivity.     

LiNi<Subscript>0.4</Subscript>Co<Subscript>0.3</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> thin film electrode by aerosol deposition

LiNi_0.4Co_0.3Mn_0.3O₂ thin film electrodes are fabricated from LiNi_0.4Co_0.3Mn_0.3O₂ raw powder at room temperature without pretreatments using aerosol deposition that is much faster and easier than conventional methods such as vaporization, pulsed laser deposition, and sputtering. The LiNi_0.4Co_0.3Mn_0.3O₂ thin film is composed of fine grains maintaining the crystal structure of the LiNi_0.4Co_0.3Mn_0.3O₂ raw powder. In the cyclic voltammogram, the LiNi_0.4Co_0.3Mn_0.3O₂ thin film electrode shows a 3.9-V anodic peak and a 3.6-V cathodic peak. The initial discharge capacity is 44.6 μAh/cm², and reversible behavior is observed in charge-discharge profiles. Based on the results, the aerosol deposition method is believed to be a potential candidate for the fabrication of thin film electrodes.     

Solid-state reactivity of iron molybdate artificially contaminated by antimony ions and its relation with catalytic activity in the selective oxidation of isobutene to methacrolein

Catalysts were prepared by impregnation of Fe₂(MoO₄)₃ with different quantities of antimony butoxide. BET surface area measurement, XRD, Mössbauer spectroscopy, CTEM-AEM, XPS and ISS were used to characterize phase and surface architectures and their changes after calcination and catalytic reaction. Before calcination, antimony was present as pure oxide or hydroxide, partly as particles and partly as an incomplete monolayer on the surface of Fe₂(MoO₄)₃. After calcination at 400°C, antimony got detached from the Fe₂(MoO₄)₃ surface and aggregated very intensively, partly as Sb₂O₄ and partly, through reaction with the iron molybdate, as a mixture of distorted FeSbO₄ and MoO₃. After reaction or calcination at 500°C, more distorted FeSbO₄ and MoO₃ are formed, separated from Fe₂(MoO₄)₃. Selective oxidation of isobutene to methacrolein was carried out on the calcined material. Impregnated catalysts show considerably improved catalytic performances compared to the pure Fe₂(MoO₄)₃ phase or mechanical mixtures of it with α-Sb₂O₄. The catalytic performances are explained by several catalytic cooperations via spillover oxygen. These cooperative effects involve all the oxide phases present in the material having worked as catalyst: Fe₂(MoO₄)₃ (pure or possibly contaminated by small amounts of antimony oxide), FeSbO₄, MoO₃ and Sb_yO_x.

     

Study of electrochemical properties and the charge/discharge mechanism for Li<Subscript>4</Subscript>Mn<Subscript>5</Subscript>O<Subscript>12</Subscript>/MnO<Subscript>2</Subscript>-AC hybrid supercapacitor

Spinel Li₄Mn₅O₁₂ was prepared by a sol–gel method. The manganese oxide and activated carbon composite (MnO₂-AC) were prepared by a method in which KMnO₄ was reduced by activated carbon (AC). The products were characterized by XRD and FTIR. The hybrid supercapacitor was fabricated with Li₄Mn₅O₁₂ and MnO₂-AC, which were used as materials of the two electrodes. The pseudocapacitance performance of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor was studied in various aqueous electrolytes. Electrochemical properties of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor were studied by using cyclic voltammetry, electrochemical impedance measurement, and galvanostatic charge/discharge tests. The results show that the hybrid supercapacitor has electrochemical capacitance performance. The charge/discharge test showed that the specific capacitance of 51.3 F g⁻¹ was obtained within potential range of 0–1.3 V at a charge/discharge current density of 100 mA g⁻¹ in 1 mol L⁻¹ Li₂SO₄ solution. The charge/discharge mechanism of Li₄Mn₅O₁₂ and MnO₂-AC was discussed.     

Adsorption of thallium cations on RuO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> electrodes

The electrochemical ion-exchange properties of RuO₂–TiO₂ film electrodes with different composition have been studied in acidic and alkaline media. Thallium-cation uptake has been observed only from the latter and its extent was found to be a function of electrode potential and composition. At potentials near 0.0 V (RHE), the amount of adsorbed Tl⁺ exhibited a maximum, and decreased with increasing potential, reaching a broad minimum in the range 0.4–0.8 V. A further increase in the electrode potential, above about 1.0 V, led to an increase of adsorbed thallium species, essentially due to deposition of a few layers of Tl(III) hydroxide. In fact, the release of the latter species was found to be much slower than that of thallium ions adsorbed at 0.0 V. For the latter, in turn, the double injection/ejection mechanism, currently accepted to explain the charge-storage in oxide electrodes, seems to be confirmed. The high Γ values attained at 0.0 V indicate that the large ionic radius of Tl⁺ does not prevent its diffusion through the thinner pore texture of the oxide coatings, possibly because of its poor hydration, related with lower charge density at the ion surfaces.     

Syndiospecific Polymerization of Styrene Using Half-Titanocene Catalyst Covalently Supported on MgCl<Subscript>2</Subscript>/AlEt<Subscript>n</Subscript>(OEt)<Subscript>3-n</Subscript>

The novel half-titanocene catalyst bearing reactive functional amino group, η⁵-pentamethylcyclopentadienyltri(p-amino-phenoxyl) titanium [Cp^∗Ti(p-OC₆H₄NH₂)₃], was easily synthesized by the reaction of η⁵-pentamethylcyclopentadienyltrichloride titanium (Cp^∗TiCl₃) with p-amino phenol in the presence of triethyl amine (NEt₃). Cp^∗Ti(p-OC₆H₄NH₂)₃ covalently anchored on MgCl₂/AlEt_n(OEt)_3-n support obtained from the reaction of triethylaluminium (AlEt₃) with the adduct of magnesium chloride (MgCl₂) and ethanol (EtOH), has been investigated and used to catalyze syndiospecific polymerization of styrene. Influences of the support structure, cocatalyst, and the molar ratio of Al in methylaluminoxane (MAO) and Ti (Al_MAO/Ti) on catalytic activity, syndiotacticity and molecular weight of the resultant polystyrene were investigated. Compared with the corresponding Cp^∗Ti(p-OC₆H₄NH₂)₃ homogeneous catalyst, a considerable increase in activity and molecular weight of syndiotactic polystyrene (sPS) was observed for the Cp^∗Ti(p-OC₆H₄NH₂)₃-MgCl₂/AlEt_n(OEt)_3-n supported catalyst even at a relatively low Al_MAO/Ti ratio of 50, and the kinetics of polymerization was stable during the reaction process.     

Nanoporous TiO<Subscript>2</Subscript> film electrode for electrocatalytic reduction of 2-pyridineethanol in ionic liquids

Nanoporous TiO₂ having enhanced surface area was synthesized by sol–gel method. On the nanoporous TiO₂ film electrode, electrocatalytic reduction of the 2-pyridineethanol in the ionic liquid electrolyte of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMI]BF₄) was investigated by cyclic voltammetry (CV). It was found that the indirect electroreduction of 2-pyridineethanol produced 2-piperidinoethanol by Ti(IV)/Ti(III) redox system on the nanoporous TiO₂ film surface. The current of cathodic reduction peak increased along with the increase of reactant concentration. The electrode reaction mechanism is called catalytic (EC′) mechanism.     

Uniform color coating of multilayered TiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> films by atomic layer deposition

Thin film optics, based on light interference characteristics, are attracting increasing interest because of their ability to enable a functional color coating for various applications in optical, electronic, and solar industries. Here, we report on the dependence of coloring characteristics on single-layer TiO₂ thicknesses and alternating TiO₂/Al₂O₃ multilayer structures prepared by atomic layer deposition (ALD) at a low growth temperature. The ALD TiO₂ and Al₂O₃ thin films were studied at a low growth temperature of 80°C. Then, the coloring features in the single-layer TiO₂ and alternating TiO₂/Al₂O₃ multilayers using both the ALD processes were experimentally examined on a TiN/cut stainless steel sheet. The Essential Macleod software was used to estimate and compare the color coating results. The simulation results revealed that five different colors of the single TiO₂ layers were shown experimentally, depending on the film thickness. For the purpose of highly uniform pink color coating, the film structures of TiO₂/Al₂O₃ multilayers were designed in advance. It was experimentally demonstrated that the evaluated colors corresponded well with the simulated color spectrum results, exhibiting a uniform pink color with wide incident angles ranging from 0° to 75°. This article advances practical applications requiring highly uniform color coatings of surfaces in a variety of optical coating areas with complex topographical structures.     

Catalytic combustion of volatile aromatic compounds over CuO-CeO<Subscript>2</Subscript> catalyst

Ce_1?x Cu _x O₂ oxide solid solution catalysts with different Ce/Cu mole ratios were synthesized by the one-pot complex method. The prepared Ce_1?x Cu _x O₂ catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H₂ temperature-programmed reduction (H₂-TPR). Their catalytic properties were also investigated by catalytic combustion of phenyl volatile organic compounds (PVOCs: benzene, toluene, xylene, and ethylbenzene) in air. XRD analysis confirmed that the CuO species can fully dissolve into the CeO₂ lattice to form CeCu oxide solid solutions. XPS and H²-TPR results indicated that the prepared Ce_1?x Cu _x O₂ catalysts contain abundant reactive oxygen species and superior reducibility. Furthermore, the physicochemical properties of the prepared Ce_1?x Cu _x O₂ catalysts are affected by the Ce/Cu mole ratio. The CeCu₃ catalyst with Ce/Cu mole ratio of 3.0 contains abundant reactive oxygen species and exhibits superior catalytic combustion activity of PVOCs. Moreover, the ignitability of PVOCs is also affected by the respective physicochemical properties. The catalytic combustion conversions of ethylbenzene, xylene, toluene, and benzene are 99%, 98.9%, 94.3%, and 62.8% at 205, 220, 225, and 225 °C, respectively.     

Synthesis of Heterogeneous Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> Nanostructured Anodes with Long-Term Cycle Stability

The 0D-1D Lithium titanate (Li₄Ti₅O₁₂) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H₂O) and protonated trititanate (H₂Ti₃O₇) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li₄Ti₅O₁₂ powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li₄Ti₅O₁₂ nanoparticles. The Li₄Ti₅O₁₂ heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate performance of 114 mAh/g at 20C.     

A Novel Coordination Polymer with Helical Chain: Synthesis and Crystal Structure of [Cu<Subscript>4</Subscript>(PMEP-Sal)<Subscript>4</Subscript>·H<Subscript>2</Subscript>O]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

Summary A novel coordination polymer, [Cu₄(PMEP-sal)₄·H₂O] _n (PMEP-sal = 4-(2′-hydroxyl benxoylhydrazinyl) ethylidene-5-methyl-2-phenyl-pyrazole-3-one), is synthesized. Single crystal X-ray analysis reveals the polymer contains tetranuclear building blocks in helical arrangement.