Electrodeposition of Al-Ti alloy on mild steel from AlCl<Subscript>3</Subscript>-BMIC ionic liquid

The electrodeposition of Al-Ti alloy on a mild steel substrate is examined in a Lewis acidic 66.7–33.3 mol% AlCl₃-1-buthyl-3-methylimidazolium chloride ionic liquid containing TiCl₄. Dense and compact Al-Ti alloy coatings with Ti content ranging from 5.3 to 11.4 at.% can be obtained under optimized conditions. The applied current densities and TiCl₄ concentration are found to play central roles in controlling the alloy compositions and surface morphologies of the resultant Al-Ti alloy coatings. Ti content in Al-Ti alloys increases with initial increase in the current density and decreases when the current density is beyond 5 mA cm^?2. In addition, the enhanced corrosion resistance of the mild steel substrate by the deposited Al-Ti alloy layers is evaluated via electrochemical techniques. The Al-Ti alloy coatings show much higher corrosion resistance than single Al coating, and this performance is improved with the increase of the Ti content.     

A novel solution for cathodic deposition of porous TiO2 films

The redox reaction between TiCl₃ and NaNO₃ to form Ti(IV) and NO₂^? prior to deposition in a specially designed TiCl₃ + NaNO₃ solution is the key step effectively promoting the cathodic deposition of porous TiO₂ films. The continuous reduction of NO₂^? to N₂ and NH₃ generates extensive OH^?, enhancing the deposition rate of TiO₂. The linear sweep voltammetric (LSV) and electrochemical quartz crystal microbalance (EQCM) studies reveal the electrocatalytic effect of oxy-hydroxyl-titanium already deposited onto the substrate for the NO₂^? and N₂ reduction. The porous and crystalline structures of as-deposited and annealed TiO₂ films are examined by field-emission scanning electron microscopic (FE-SEM), transmission electron microscopic (TEM) and selected area electron diffraction (SAED) analyses.     

C-NMR study of Ti(IV) species formed by Cp*TiMe3 and Cp*TiCl3 activation with methylaluminoxane (MAO)

Using ¹³C- and ¹H-NMR spectroscopy, titanium(IV) species formed in the catalytic systems Cp*TiMe₃/MAO and Cp*TiCl₃/MAO (Cp*=C₅(CH₃)₅) in toluene and chlorobenzene were studied within the temperature range 253-293 K and at Al/Ti ratios 30-300. It was shown that upon activation of Cp*TiMe₃ with methylaluminoxane (MAO) mainly the ‘cation-like’ intermediate Cp*Me₂Ti⁺←Me⁻Al(MAO) (2) is formed. Three types of titanium(IV) complexes were identified in Cp*TiCl₃/MAO catalytic system. They are methylated complexes Cp*TiMeCl₂ and Cp*TiMe₂Cl, and the ‘cation-like’ intermediate 2. Complex 2 dominates in Cp*TiCl₃/MAO system in conditions approaching to those of practical polymerization (Al/Ti ratios more than 200). According to the EPR measurements, the portion of EPR active Ti(III) species in the Cp*TiCl₃/MAO system is smaller than 1% at Al/Ti=35, and is about 10% at Al/Ti=700.     

Synthesis and characterization of Ti(IV)-substituted calcium hydroxyapatite particles by forced hydrolysis of Ca(OH)2-Na5P3O10-TiCl4 mixed solution

Ti(IV)-substituted calcium hydroxyapatite (TiHap) particles were prepared by aging Ca(OH)₂, TiCl₄, and sodium triphosphate (sodium tripolyphosphate, Natpp: Na₅P₃O₁₀) mixed solution at 100 °C for 18 h. The ellipsoidal secondary TiHap particles with ca. 100～150 nm in length composing by aggregation of small ellipsoidal primary particles with ca. 20 nm in length were produced at atomic ratio of Ti/(Ca+Ti) [X_Ti]≦0.2. The in situ IR spectra of these TiHap particles exhibited very small bulk OH^? band at 3,570 cm^?1. This result indicated that the TiHap particles were formed by aggregation of fine primary particles and OH^? ions along with c-axis in the primary particles were disordered. The TiHap particles with Ca/P atomic ratio larger than theoretical value of 1.67 did not exhibit surface P–OH groups at 3,659 and 3,682 cm^?1. The diffuse reflectance UV spectra of TiHap particles revealed that these particles have a UV absorption property, especially fabricated at X_Ti?=?0.1. The particles prepared at X_Ti?=?0.6 and 0.8 were amorphous and nanoparticles with 5～10 nm in diameter, but those precipitated at X_Ti?=?1.0 were poorly crystallized anataze-type TiO₂ nanoparticles.     

Morphology-controlled synthesis of Ti-doped α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanorod arrays as an efficient photoanode for photoelectrochemical applications

Few reports have been published on the optimization of nanostructures while doping with the Ti (Ti³⁺/Ti⁴⁺) elemental. Here, Ti-doped α-Fe₂O₃ nanorod arrays prepared via the hydrothermal method with the addition of TiCl₃ as the Ti source and urea as the morphological regulator were used as photoanodes in photoelectrochemical cells. In the process of a hydrothermal reaction, Ti elemental was incorporated into α-Fe₂O₃ photoanodes using TiCl₃ as precursor and urea was used as the morphological regulator to assist α-Fe₂O₃ to form nanorod arrays. The photoelectrochemical performance of the as-prepared Ti-doped α-Fe₂O₃ nanorod array (TF1) photoanodes exhibited a remarkable photocurrent of 0.22 mA cm^?2 (275 times higher than that of the undoped α-Fe₂O₃ nanorod arrays) at 1.23 V (vs. RHE) and a 150-mV cathodic shift of photocurrent onset potential. The enhanced photoelectrochemical performance was ascribed to the synergistic effect of the one-dimensional nanoarray structure and the Ti elemental doping, which increased donor density and reduced photogenerated electron–hole recombination.     

Determination of neptunium in a reprocessing plant by an on-line solid-phase extraction/electrochemical detection system

In this study, a flow-based electrochemical detection system coupled to a solid-phase extraction column was developed for the determination of neptunium in the presence of Pu(IV). Np(V) in the sample solution was completely oxidized to Np(VI) via electrolysis using a column electrode composed of carbon fibers. The column electrode effluent was then loaded onto a TEVA^® column, and subsequently onto a UTEVA^® column using 3 mol L^?1 HNO₃. Pu(IV) was retained on the TEVA column and separated from Np(VI), while Np(VI) was retained on the UTEVA column. Np(VI) was eluted from the UTEVA column with 0.01 mol L^?1 HNO₃ and then introduced directly into a flow-through electrolysis cell. An electrochemical amperometric method with a working potential of +0.1 V (vs. Ag/AgCl) was used to detect Np(VI). The current produced due to the reduction of Np(VI) was continuously monitored and recorded, and the Np concentration was calculated from the peak area. The relative standard deviation of 10 analyses was 2.4 % for an Np solution (0.50 mg L^?1) containing 1.0 μg Np. The detection limit, which was determined to be three times the standard deviation, was 35 μg L^?1 (70 ng Np).     

Electrodeposition of aluminum–hafnium alloy from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrochemistry of Hf(IV) and the electrodeposition of Al–Hf alloys were examined in the Lewis acidic 66.7–33.3 mol% aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt containing HfCl₄. When cyclic staircase voltammetry was carried out at a platinum disk electrode in this melt, the deposition and stripping waves for Al shifted to negative and positive potentials, respectively, suggesting that aluminum stripping is more difficult due to the formation of Al–Hf alloys. Al–Hf alloy electrodeposits containing ~13 at.% Hf were obtained on Cu rotating wire and cylinder electrodes. The Hf content in the Al–Hf alloy deposits depended on the HfCl₄ concentration in the melt, the electrodeposition temperature, and the applied current density. The deposits were composed of dense crystals and were completely chloride-free. The chloride-induced pitting corrosion potential of the resulting Al–Hf alloys was approximately +0.30 V against pure aluminum when the Hf content was above 10 at.%.     

Alloying during codeposition of copper and tin out of silicofluoride electrolytes

A technique for obtaining binary Cu-Sn alloys containing 20–35 mol % Sn is proposed. The technique—the electrochemical deposition out of silicofluoride electrolytes—ensures a high deposition rate of coatings (25–50 μm h^?1). The formation of intermetallic compound Cu₁₀Sn₃ is found to occur at a high current density, in conditions of the tin reduction depolarization and the copper reduction superpolarization. The alloys consist of submicron grains. Apart from crystalline Cu₁₀Sn₃, they include x-ray-amorphous tin (2–12 mol %) and tin oxides (≤1–3 mol %). The alloys feature high hardness (4200 MPa), corrosion resistance, and solderability.     

Fabrication of self-organized TiO2 nanotube arrays for photocatalytic reduction of CO2

The photocatalytic conversion of CO₂ and H₂O to alcohols was achieved using self-organized TiO₂ nanotube arrays (TNAs), which were prepared by electrochemical anodization of Ti foils in 1 M (NH₄)₂SO₄ electrolyte containing 0.5 wt% NH₄F. Experimental results revealed that the morphology and structure of self-organized TNAs could be strongly influenced by the applied voltage and anodization temperature, and the optimized TNAs were prepared by electrochemical anodization of Ti foils under optimal conditions (i.e., at 20 V for 2 h at 30 °C). The as-prepared TNAs were amorphous and could be transformed to anatase phase during the thermal treatment at 450 °C in air for 3 h. By using the annealed TNAs as a photocatalyst, the photocatalytic reduction of CO₂ to alcohol, predominately methanol and ethanol, was demonstrated under Xenon lamp illumination. Based on the photocatalytic measurements, the production rates of methanol and ethanol were calculated to be ～10 and ～9 nmol cm^?2 h^?1, respectively. In addition, the formation mechanism of methanol and ethanol was also tentatively proposed.     

高分子固载化Lewis酸催化剂——聚苯乙烯-三氯化铝/四氯化钛复合物

<正> 均相催化剂的固载化是目前催化剂研究方向之一。Skct等首次将BF_5和AlCl_3分别与苯乙烯反应制成高分子催化剂,对酯化、缩醛、缩酮等有机反应具有良好的催化作用。我们曾将四氯化钛与聚苯乙烯反应制成一种稳定复合物,有良好的催化效能。为了改进其重复使用性能,本文将等摩尔的AlCl_3,和TiCl_4的Lewis酸同时与聚苯乙烯交     

Enhancing effect of boron trifluoride diethyl etherate electrolytes on capacitance performance of electropolymerized poly[poly(<Emphasis Type="Italic">N</Emphasis>-vinyl-carbazole)] films

In this paper, poly[poly(N-vinyl-carbazole)] (PPVK) films electrodeposited in tetrahydrofuran (THF) containing 12 % boron trifluoride diethyl etherate (BFEE) were studied as electrode active material for supercapacitors. The morphology and thermal property were characterized by SEM, atomic force microscopy (AFM), and thermogravimetry (TG), respectively. The electrochemical capacitive behaviors of the PPVK films were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The electrochemical results showed that the specific capacitance of PPVK films in CH₃CN solution was about 126 mF cm^?2 at 1.5 mA cm^?2 and the capacitance retention was only 14.4 % after 1000 cycles. It was exciting to improve the specific capacitance up to 169.3 mF cm^?2 at 1.5 mA cm^?2 and to make the cyclic stability increase to 81.8 % capacitance retention after 5000 cycles when the equivalent BFEE was added into the CH₃CN solution containing 0.05 M Bu₄NBF₄ electrolyte. These results clearly demonstrated that BFEE was an efficient promoter for the enhancement of the capacitance performance of PPVK films. Therefore, with the help of BFEE electrolyte, the PPVK films have potential application as capacitive materials in high-performance energy storage devices.     

(η5-Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene

An equimolar mixture of Cp*Ti(CH₃)₃ (2) and Ph₃C⁺[B(C₆F₅)₄]^? (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 10⁷ g PS (mol Ti)^?1 (mol styrene)^?1 h^?1. Both activity and syndioselectivity can be increased using tri–isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl₃/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.     

Plutonium oxidation state distribution in natural clay and goethite

Distribution of Pu(IV) and Pu(V) oxidation states at trace initial concentrations (10^?10–10^?11 mol L^?1) was studied in a liquid- and solid-phase of natural clay and goethite systems. Experiments showed an increase in the concentration of Pu(III) up to 11% at pH 5 in solids of the natural clay ?0.1 mol L^?1 NaNO₃ system containing Pu(IV) after 7-day contact. A kinetic sorption/reduction experiment with goethite suspensions (0.01 mol L^?1 NaNO₃ containing Pu(V)) indicated the presence of Pu(III) in the solids up to 15%.     

Über Cyanatverbindungen und deren reaktives Verhalten. XXXI [1]. Solvatfreies Titan(IV)-thiocyanat und einige abgeleitete Tetrathiocyanato-bis(ligand)-titan(IV)-Komplexe

Cyanates and Their Reactive Behaviour. XXXI. Solvate-free Titanium(IV) Thiocyanate and Some Related Tetrathiocyanato-bis(ligand) Titanium(IV) Complexes TiCl₄ and [TiCl_a(NCS)_bL₂] compounds react with alkali thiocyanates in tetrahydrofurane or acetonitrile to monomeric tetrathiocyanato-bis(ligand)titan(IV) complexes (a = 1, 2, 3; b = 3, 2, 1; L = CH₃CN, C₄H₈O), also NH₄[TiCl(NCS)₄(THF)] · 2 THF is formed. Desolvatation of [Ti(NCS)₄(THF)₂] leads to [Ti(NCS)₄]_x. The prepared compounds are characterized by analytical data, IR and electron spectra, and conductivity measurements.     

Phosphaniminato-Komplexe von Titan(IV). Die Kristallstrukturen von [TiCl3(NPEt3)]2, [TiCl3(NPEt3)(THF)2] und [TiCl4{Me2Si(NPEt3)2}]

Phosphoraneiminato Complexes of Titanium(IV). Crystal Structures of [TiCl₃(NPEt₃)]₂, [TiCl₃(NPEt₃)(THF)₂], and [TiCl₄{Me₂Si(NPEt₃)₂}] [TiCl₃(NPEt₃)]₂ ( 1 ) is formed from titanium(IV) chloride and the silylated phosphaneimine Me₃SiNPEt₃ in dichloromethane as reddish-brown, moisture-sensitive crystals. According to the crystal structure analysis these crystals show centrosymmetric Ti₂N₂ four-membered rings with Ti–N distances of 184.7 and 210.3 pm. With tetrahydrofurane 1 forms yellow, moisture sensitive crystals of the solvate [TiCl₃(NPEt₃)(THF)₂] ( 2 ), in which the titanium atom is octahedrally coordinated. The THF molecule which is in trans position to the phosporaneiminato ligand realizes but a very weak Ti–O bond of 238.0 pm, the cis THF molecule shows a Ti–O distance of 213.7 pm. With 173.4 pm along with a TiNP bond angle of 160.0° the TiN distance is very short. The bis(phosphaneimine) complex [TiCl₄{Me₂Si(NPEt₃)₂}] ( 3 ) is formed as colourless crystals in low yield in the reaction of titanium(IV) chloride with Me₃SiNPEt₃ and trimethylcyclopentadienylsilane. In 3 the titanium atom is surrounded by four chlorine atoms in a distorted octahedral fashion and by the two N atoms of the Me₂Si(NPEt₃)₂ molecule with TiN distances of 205.6 pm.     

Spectroscopic,electrochemical, and structural aspects of the Ce(IV)/Ce(III) DOTA redox couple chemistry in aqueous solutions

The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, pointing out a stabilization of ~13 orders of magnitude for the Ce(IV)DOTA complex, as compared to Ce(IV)_aq. The Ce(III)DOTA after electrochemical oxidation yields a Ce(IV)DOTA complex with a t_1/2 ~3 h and which is suggested to retain the “in cage” geometry. Chemical oxidation of Ce(III)DOTA by diperoxosulfate renders a similar Ce(IV)DOTA complex with the same t_1/2. From the electrochemical measurements, one calculates logK (Ce(IV)DOTA^2?) ~ 35.9. Surprisingly, when Ce(IV)DOTA is obtained by mixing Ce(IV)_aq with DOTA, a different species is obtained with a 2 : 1(M : L) stoichiometry. This new complex, Ce(IV)DOTACe(IV), shows redox and spectroscopic features which are different from the electrochemically prepared Ce(IV)DOTA. When one uses thiosulfate as a reducing agent of Ce(IV)DOTACe(IV), one gets a prolonged lifetime of the latter. The reductant seems to serve primarily as a coordinating ligand with a geometry which does not facilitate inner sphere electron transfer. The reduction process rate in this case could be dictated by an outer sphere electron transfer or DOTA exchange by S₂O₃^2?. Both Ce(IV)DOTA and Ce(IV)DOTACe(IV) have similar kinetic stability and presumably decompose via decarboxylation of the polyaminocarboxylate ligand.     

Effect of molten salt synthesis temperature on TiO<Subscript>2</Subscript> and Li cycling properties

In this project, we synthesized TiO₂ compounds through the molten salt method (MSM) using Ti(IV) oxysulfate, as the Ti source. Molten salts in the ratio of 0.375 M LiNO₃:0.180 M NaNO₃:0.445 M KNO₃ were added and heated at temperatures of 145, 280, 380, and 480 °C for 2 h in air, respectively. A part of the sample prepared at 145 °C was further reheated to 850 °C for 2 h in air. X-ray diffraction studies showed that the amorphous phase was obtained when the sample was prepared at 145 °C, and polycrystalline to crystalline anatase phase was formed when heated from 280 to 850 °C, which is complementary to the results of selected area electron diffraction studies. Electrochemical properties were studied using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy at a current density of 33 mA g^?1 (0.1 C rate) and a scan rate of 0.058 mV s^?1, in the voltage range 1.0–2.8 V vs. Li. Electrochemical cycling profiles for the amorphous TiO₂ samples prepared at 145 °C showed single-phase reaction with a low reversible capacity of 65 mAh g^?1, whereas compounds prepared at 280 °C and above showed a two-phase reaction of Li-poor and Li-rich regions with a reversible capacity of 200 mAh g^?1. TiO₂ produced at 280 °C showed the lowest capacity fading and the lowest impedance value among the investigated samples.     

Komplexe in TiCl3-Alkohol-Lösungen

Complexes in TiCl₃-Alcohol Solutions. Whereas in aqueous solution there exist both [Ti · aq₆]³⁺ and [Ti · aq₄Cl₂]¹⁺ ions, in methanol and ethanol only [Ti(ROH)₆]³⁺ ions and in isopropanol only [Ti(ROH)₄Cl₂]¹⁺ ions are present. A crystalline [Ti(MeOH)₆]Cl₃ complex has been prepared.     

Interfacial and bulk processes during oxide growth on titanium in ethylene glycol-based electrolytes

Anodic oxidation has proven to be a promising route for the growth of self-ordering oxide nanotubes on Ti, the best results being obtained in ethylene glycol (EG)-based electrolytes with the addition of fluoride and small amounts of water. In the present paper, emphasis is put on the investigation of barrier film growth and dissolution on Ti in EG electrolytes with the addition of H₂O (0.3–2.4 M) and NH₄F (0.015–0.17 M) using electrochemical and surface analytical techniques. Steady-state current–potential curves and electrochemical impedance spectra as depending on potential (?0.1/5.0 V vs. AgCl/Ag), water and fluoride content have been registered. In addition, the chemical composition of the surface of the oxides obtained at 0.1 and 1.0 V has been estimated by X-ray photoelectron spectroscopy (XPS). XPS analysis revealed the presence of a non-stoichiometric oxide containing mainly Ti⁴⁺ and a certain amount of Ti³⁺, with a certain degree of hydroxylation. Estimates of the total thickness of the oxide from the XPS data using a dual layer model are also presented. A kinetic model of the process is advanced to quantitatively interpret the electrochemical and surface analytical results.     

Tetraphenylarsonium-tetrachloromonoazidotitanat (IV); Darstellung,IR-Spektrum und Kristallstruktur von (AsPh4)2 [TiCl4N3]2

Tetraphenylarsonium Tetrachloromonoazidotitanate(IV); Preparation, I.R. Spectrum, and Crystal Structure of (AsPh₄)₂[TiCl₄N₃]₂ The title compound was obtained from TiCl₄ and AsPh₄N₃ in H₂CCl₂ solution in form of yellow crystals. Its crystal structure was determined with X-ray diffraction data and was refined to a residual index of R = 4.2%. (AsPh₄)₂[TiCl₄N₃]₂ crystallizes in the space group P1 with one formula unit per unit cell. The [TiCl₄N₃]₂^? ion is situated on a crystallographic inversion center and beyond that fulfills the point symmetry C_2h in good approximation. The two Ti atoms are linked via the α-N atoms of the azido groups forming a planar (TiN)₂ ring. The azido groups are inclined by 20° towards the ring plane. The i.r. Spectrum was recorded and assigned.