Development of 3 DOF Ultrasonic Vibration Tool for Elliptical Vibration Cutting of Sculptured Surfaces

A new machining method is proposed to obtain sculptured mirror surfaces by applying elliptical vibration cutting. The tool is vibrated elliptically unlike rotated end mills and fed along the sculptured surface in the proposed method. A 3 DOF ultrasonic vibration tool is developed, which can generate an arbitrary ultrasonic elliptical vibration in the 3D space so that it is suitable to machine the 3D sculptured surfaces. A precision machine tool is also developed, and the proposed method is successfully applied to mirror surface machining of hardened die steel.     

New thio-compounds as corrosion inhibitor for steel in 1 M HCl

Some S-containing compounds newly synthesised have been tested as inhibitors for the corrosion of steel in 1 M HCl solution. Weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods are used. The inhibiting action increases with the concentration of the compounds tested. The highest efficiency 95% is obtained at 10⁻⁴ M of [(11-hydroxyundecyl)thio]acetic acid (3 and 4). We note good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS). Polarisation measurements show also that 3 and 4 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. 3 adsorbs on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied between 308 K and 353 K.     

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives: Design,synthesis, crystal structures,electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1·2 and 1·3₂, respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1·2 and 1·3₂ and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV–Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1·2 and 0.40 eV for 1·3₂. Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.     

Experimental and theoretical calculations on corrosion inhibition of steel in 1 M H2SO4 by crown type polyethers

The corrosion inhibitive efficiencies of two crown type polyethers, namely dibenzo-bis-imino crown ether (C-1) and dibenzo-diaza crown ether (C-2), which are macrocyclic Schiff base and its reduced form (macrocyclic amine), respectively, for the steel in 1 M H₂SO₄ have been investigated by Tafel extrapolation and linear polarization methods. Corrosion and adsorption isotherm parameters were determined from current-potential curves. The studies show that C-1 and C-2 inhibit the corrosion of the steel in H₂SO₄ solution. Semiempirical AM1 method was used for theoretical calculations. The obtained results of these calculations for the compounds were found to be consistent with the experimental findings.     

Synthesis and characterization of novel polythiophenes bearing oligo(ethylene glycol) spacers and crown ethers

Two novel thiophene containing monomers (TM): 3-methyltetra(oxyethylene)oxy-4-methylthiophene (TM1) and 3-(((2-aminobenzo-18-crown-6-ethyl)triethoxy)oxy)-4-methylthiophene (TM2) were synthesized and characterized. Both monomers were polymerized in the presence of FeCl₃ to give the corresponding copolymer (CPT1). TM2 was also copolymerized in the presence of 3-dodecylthiophene to lead a second copolymer (CPT2). On the other hand, TM1 and TM2 were homopolymerized under the same reaction conditions to give poly[3-methyltetra(oxyethylene)oxy-4-methylthiophene] (PT1) and poly[3-(((2-aminobenzo-18-crown-6-ethyl)triethoxy)oxy)-4-methylthiophene] (PT2), where the former was used as reference compound. Solvatochromic and thermochromic behaviors of these polymers were investigated. All polymers exhibited solvatochromism; in a mixture of chloroform–methanol 20:80, CPT1 gives a violet solution and its polymer backbone adopts a planar conformation. By contrast, in chloroform CPT1 adopts a twisted conformation, giving an orange solution. This copolymer exhibits also an extended conjugation length in the solid state at room temperature (dark red) and a less conjugated conformation after heating (yellow). CPT2 shows a similar thermochromic behavior as CPT1 in chloroform, but in the solid state its color changes from dark red to orange.     

Two Cd(II) coordination polymers based on asymmetrical Schiff-base ligand with five- and six-membered N-containing heterocyclic rings: Synthesis,crystal structures and luminescent properties

Two cadmium inorganic–organic hybrid coordination polymers [CdL(SCN)₂]_n (1) and [CdLI₂]_n (2), have been synthesized and characterized by IR spectroscopy, elemental analysis, XRPD, thermogravimetric (TG) analyses and X-ray crystallography, where L is 4-(pyridine-4-yl)methyleneamino-1,2,4-triazole. Asymmetrical Schiff-base ligand L acts as a bidentate bridging ligand to bind two Cd(II) centers through two terminal N_triazolyl and N_pyridyl donors in polymers 1 and 2. Polymer 1 displays a new 3D inorganic–organic hybrid network generated through the coordination interactions between Cd-(1,3-μ-SCN⁻) 2D inorganic sheets and bidentate bridging ligands. The structure of polymer 2 is a 3D chiral supramolecular framework which contains helical chains on 2₁ axis. Each Cd(II) center is coordinated by two ligands and two I⁻ donors to attain a distorted tetrahedral environment. The luminescent properties of polymers 1 and 2 were investigated in the solid state at room temperature.     

Synthesis and characterization of efficient orange-red emitting poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole unit

A series of the statistical copolymers of tetradecyloxy-3,5-bis-{2-(4-bromo-phenyl)-[1,3,4]oxadiazole}-benzene (4), 1,4-didecyloxy-2,5-diiodobenzene (5) and 1,4-dodecyloxy-2,5-divinylbenzene (6), for efficient light emitting diode were synthesized. As the feed ratio of compound 4 decreased, the absorption band at 320–360 nm decreased in the UV–vis spectra. In addition, as the composition of compound 4 decreased, the absorption intensity ratio at 1541 cm⁻¹ decreased in the FT-IR spectra. The photoluminescence and electroluminescence emission color of P showed green-yellow color (λ_max = 552 nm). However, the maximum wavelength of photoluminescence and electroluminescence of P1 and P2 were 581 and 583 nm, respectively, which were dramatically red-shifted than that of P. Moreover, these values were almost the same as the values of P3 (580 nm). It is concluded that the energy transfer from high energy oxadiazole segments to low energy alkoxy-PPV segments occurred completely. The efficiency of ITO/P2/Al was 0.0181%, which is the best efficiency among the device based on the copolymers. This is presumably due to that P2 has the best balanced hole- and electron-injection/transporting properties among the copolymers.     

Syntheses,structures, and luminescent properties of cadmium (II) complexes: 3D supramolecular [Cd(phen)(NO3)(NO2)(H2O)]n and Cd(phen)2(NO3)(NO2) constructed by π–π stacking interactions

Two novel complexes [Cd(phen)(NO₃)(NO₂)(H₂O)]_n (1) and Cd(phen)₂(NO₃)(NO₂) (2) (phen = 1,10-phenanthroline) have been synthesized by the reductive reaction of metal source Cd(NO₃)₂·4H₂O with phen and benzidine in the mixed solution of DMF, ethanol and water. Crystal structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Complex 1 is a one-dimensional (1D) zig-zag infinite chain in which (phen)Cd^(II) units were bridged by two O atoms of NO₂⁻. The three-dimensional (3D) supramolecular structure of 1 is constructed through hydrogen-bond and aromatic π–π stacking interactions between adjacent metal–organic polymeric coordination chains. Complex 2 is a mononuclear structure, and self-assembled through π–π stacking interactions to form a three-dimensional (3D) supramolecular structure. The complex 1 exhibits luminescent property in the near-UV at room temperature in solutions of DMSO and DMF with the emission energy following the order DMF < DMSO, which might be ascribed to the presence of a highly polarized ground state. Complexes 1 and 2 have blue-purple luminescence at room temperature in the solid state. The blue-purple luminescence of the complexes is due to π* → π transition of phen.     

Synthesis and photovoltaic properties of two new unsymmetrical zinc-phthalocyanine dyes

Two new soluble unsymmetrical zinc-phthalocyanine derivatives (PC-HY1, PC-HY2) with D-π-A structure bearing three tert-butylphenyl or tert-butylthienyl groups and cyanoacrylic acid groups were synthesized through a low-cost “anhydride” method. The photophysical, electrochemical and photovoltaic properties of the phthalocyanine derivatives were studied. The two phthalocyanine derivatives showed strong and broad absorption in the UV and red/near-infrared (IR) region, especially for PC-HY2. The electrochemical properties indicated that the two phthalocyanine derivatives are latent materials for dye-sensitized solar cells. Under the illumination of AM 1.5, 100 mW cm⁻², dye-sensitized solar cells based on PC-HY1 and PC-HY2 showed power conversion efficiency (PCE) of 0.79% and 1.09%, respectively.     

Preparation and ionophoric properties of coronene fluoroionophores containing azacrown and calix[4]azacrown ethers

Novel coronene fluoroionophores, N,N′-dipropyl-5,11-bis[4-(1-aza-18-crown-6)phenyl]cornene-2,3,8,9-tetracarboxy diimide (4), and N,N′-dipropyl-5,11-bis[4-(calix[4]azacrown-5-crown-5)phenyl]coronene-2,3,8,9-tetracarboxy diimide (6), were prepared by reacting N,N′-dipropyl-5,11-bis(p-chlorophenyl)coronene-2,3,8,9-tetracarboxy diimide (3) with 1-aza-18-crown-6 or calix[4] azacrown-5-crown-5. Alternating copolymers, 5 and 7, with a similar repeating unit were prepared by reacting 7,16-diaza-18-crown-6 or calix[4]bisazacrown-5 with compound 3. The fluoroionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions. The model and polymeric fluoroionophores exhibited significant decreasing fluorescence effects with K⁺, Ag⁺ and Ba²⁺, which were attributed to photoinduced charge transfer (PCT).     

Synthesis and third-order nonlinear optical studies of a novel four-coordinated organoboron derivative and a bidentate ligand: The effect of the N → B coordinative bond

The third-order nonlinear optical characterization of a new boronate (2) derived from 4-dimethylaminocinnamaldehyde was performed by third-harmonic generation (THG) at the infrared wavelength of 1550 nm. Compound 2 was prepared from the reaction of diphenylboronic acid and the bidentate ligand (1) and characterization was made through UV, IR, ¹H, ¹¹B, and ¹³C NMR and X-ray diffraction. The THG experiments showed that the N → B coordinative bond in 2 enhanced the second molecular hyperpolarizability of the type γ⁽³⁾(−3ω, ω, ω, ω) by a factor of three with respect to the value exhibited by the ligand 1. On the other hand, Z-scan studies at 800 nm (femtosecond (fs) pulses) also showed that such coordinative bond increased the nonlinear absorption (two-photon absorption (TPA)) in 2 with respect to 1. These studies demonstrate that the N → B coordinative bond facilitates the polarization of the electronic π-system, a situation that optimizes the third-order NLO response. Results on the excited state absorptions in these compounds are also presented.     

High temperature fracture experiments on tungsten–rhenium alloys

A big problem when using tungsten as plasma facing components in a future fusion reactor is the very low fracture toughness at low temperatures. Tungsten–rhenium alloys outclasses other tungsten-based materials in terms of increased ductility. We study the reason for this positive effect by investigating the influence of rhenium on the fracture process of tungsten–rhenium alloys at different temperatures (between room temperature and 900 °C). The experiments are performed in a furnace-equipped tensile testing machine with a vacuum chamber, which allows us to perform fracture experiments at elevated temperature without oxidizing the material. Antecedent and subsequent electron backscattered diffraction scans are used to analyse the extent of plastic deformation and the interaction of plastic deformation and the fracture process. Furthermore, the consequences of recrystallization on the fracture process of tungsten–rhenium alloys will be analysed.     

Corrosion inhibition of brass in presence of terdentate ligands in chloride solution

The inhibition of two terdentate ligands, 2-[(E)-pyridin-2-ylimino)methyl)]phenol and 2-[(pyridin-2-ylamino)methyl]phenol, abbreviated L₁ and L₂ respectively, on the corrosion of brass in 0.10 M NaCl solution under various conditions, has been studied by means of the potentiostatic polarization and AC impedance methods. The studies show that terdentate ligands, L₁ and L₂ inhibit the corrosion of brass in chloride solution and that the inhibiting efficiency increases with an increase in their concentrations. Self-assembled films of these substances were also prepared on the brass surface. These films improved significantly the protecting ability of brass surface to corrosion in 0.10 M NaCl solution. When the films were modified with benzotriazole (BTA), the quality and corrosion resistance of films improved markedly.     

Polarization-dependent electrolyte electroreflectance study of Cu2ZnSiS4 and Cu2ZnSiSe4 single crystals

Polarization-dependent electrolyte electroreflectance (EER) measurements were carried out on the oriented Cu₂ZnSiS₄ and Cu₂ZnSiSe₄ single crystals at room temperature. Thin blade single crystals of Cu₂ZnSiS₄ and Cu₂ZnSiSe₄ were grown by chemical vapor transport technique using iodine as a transport agent. Laue pattern normal to the basal plane of the as-grown crystal revealed the formation of orthorhombic structure with the normal along [2 1 0] and the c axis parallel to the long edge of the crystal platelet. The polarized EER spectra in the vicinity of the direct band edge of Cu₂ZnSiS₄ displayed distinct structures associated with transitions from two upper-most valence bands to the conduction band minimum at Γ point. In the E⊥c configuration, the feature designated as E_A ∼ 3.345 eV was detected and for Е‖c, only E_B ∼ 3.432 eV appeared. For Cu₂ZnSiSe₄, three features denoted as E_A, E_B, and E_C at around 2.348, 2.406 and 2.605 eV, respectively, were recorded for E⊥c polarization, whereas in the Е‖c, only E_B and E_C were the allowed transitions. Based on the experimental observations and a recent band-structure calculation by Chen et al. [Phys. Rev. B 82 (2010) 195203], plausible band structures near the direct band edge of Cu₂ZnSiS₄ and Cu₂ZnSiSe₄ have been proposed.     

Influence of cluster composition on NLO properties of neutral cubane-like heterothiometallic clusters

A series of new candidates as nonlinear optical materials, tetra-nuclear heterobimetallic clusters [MOS₃M₃′Y(PPh₃)₃] (M = Mo, M′ = Ag, Y = Br 1; M = W, M′ = Ag, Y = I 2; M = Mo, M′ = Cu, Y = I 3; M = W, M′ = Cu, Y = I 4), have been synthesized by newly developed ligand-redistribution reaction for third-order nonlinear optical (NLO) studies. Single-crystal X-ray diffraction shows that clusters [MoX(μ₃-S)₃(μ₃-Br)(AgPPh₃)₃] 1 and [WX(μ₃-S)₃(μ₃-I)(CuPPh₃)₃] 4 (X = O_0.5S_0.51, O 4) adopt an isomorphous neutral cubane-like skeleton. Their optical nonlinearities were measured by Z-scan technique with an 8 ns pulsed laser at 532 nm. These clusters were found to exhibit effective nonlinear absorption, self-focusing effects and large optical limiting capabilities. The effective NLO susceptibilities χ⁽³⁾ and the corresponding second-order hyperpolarizabilities γ of these clusters are also reported. The influence of cluster composition on NLO properties has been discussed accordingly.     

Synthesis,photophysics, electrochemical and electroluminescent properties of divinylene compounds with phthalimide moieties

Three new divinylene compounds F, C and P which contained fluorene, carbazole and phenylene as central unit, respectively, and terminal phthalimide groups were synthesized by Heck coupling. The alkyl or alkoxy chains attached to the central unit as well as the cyclohexyl ring attached to the terminal phthalimides render the samples very soluble in common organic solvents. They had relatively low glass transition temperatures (T_g's), being in the range of 54–81 °C. P was stable up to about 200 °C while F and C were stable up to 300 °C. The absorption maximum was located at 387–440 nm with optical band gap of 2.48–2.56 eV. They emitted blue-green light with emission maximum at 484–562 nm. P showed the most red-shifted absorption and emission maximum. The HOMO and LUMO levels of the compounds, estimated from their cyclic voltammograms, were −6.42 to −5.58 eV and −3.06 to −2.99 eV, respectively, from which their band gaps were estimated to be 3.36 eV, 2.68 eV, and 2.52 eV. The emission spectra and performance of the EL devices, using blends of the compounds and PVK as emitting layer, also depended strongly on the compounds. The P device emitted green light (530 nm) with maximal luminance and current efficiency being at 1358 cd/m² and 0.57 cd/A, while those of the F device were green-blue (490 nm), 593 cd/m² and 0.22 cd/A.     

Mercaptopyrimidines as inhibitors of carbon dioxide corrosion of iron

The inhibition activity of 2-mercaptopyrimidine (I), 2-mercapto-4-methylpyrimidine hydrochloride (II), 2-mercapto-4,6-dimethylpyrimidine (III) and its hydrochloride (IV) upon carbon dioxide corrosion of iron has been studied in a wide range of concentrations at 40-90 °C using electrochemical and mass-spectrometry methods. High activity has been found for all compounds (P = 80-99%) at very low concentrations (0.02-5 mg/l). Adsorption of inhibitor by metal not only blocks its surface but changes the reaction mechanism as well. Charge transfer is the limiting stage of both cathode and anode reactions. The title compounds can be considered as inhibitors of what is a mixed type with prevailing effect on the anode reaction.     

Fine tuning the HOMO energy levels of polythieno[3,4-b]thiophene derivatives by incorporation of thiophene-3,4-dicarboxylate moiety for photovoltaic applications

To lower the HOMO (highest occupied molecular orbital) energy level of polythieno[3,4-b]thiophene (∼−4.5 eV), a series of ester-functionalized polythieno[3,4-b]thiophene derivatives (P1–P3) were designed and synthesized by Stille cross coupling reaction. The resulting copolymers exhibited broad and strong absorption bands from visible to near infrared region with low optical band gaps of 1.23–1.42 eV. Through cyclic voltammetry measurements, it was found that the HOMO energy levels of the copolymers gradually decreased with increasing the content of the thiophene-3,4-dicarboxylate moiety, i.e. −4.91 eV for P1, −5.00 eV for P2, and −5.11 eV for P3. Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as electron acceptor were investigated. Among the three copolymers, P1 exhibited the best photovoltaic performance with an open circuit voltage (V_oc) of 0.54 V, a short circuit current density (I_sc) of 3.3 mA/cm², a fill factor (FF) of 0.57, and a power conversion efficiency (PCE) of 1.02%. A high V_oc up to 0.71 V was achieved in the solar cell based on a P3:PCBM blend.