Mesogenic lanthanoid metal complexes of a non-mesogenic Schiff-base, N,N′-di-(4-hexadecyloxysalicylidene)-l′,8′-diamino-3′,6′-dioxaoctane

A non-mesogenic Schiff-base, N,N′-di-(4-hexadecyloxysalicylidene)-l′,8′-diamino-3′,6′-dioxaoctane, H₂dhdsdd (H₂L²), was synthesized, structure studied by elemental analyses and mass, NMR and IR spectra and ligated to some Ln^III metal ions that yielded mesogenic (SmA/N) Ln^III complexes of the general composition, [Ln₂(L²H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L²H₂) to the Ln^III ions through two phenolate oxygens, rendering the overall geometry around Ln^III to distorted mono-capped octahedron.     

Effect of the ligand on the properties of emitting materials: Pentacoordinated 8-hydroxyquinoline aluminum complexes

Two series of pentacoordinated complexes, AlMq₂q′ and Alq₂q′ (q is 8-hydroxyquinoline, Mq is 2-methyl-8-hydroxyquinoline and q′ is phenolato ligand), were synthesized, and assessed as potential emitting materials in thin film (photoluminescence, PL) and electroluminescent (EL) device. EL devices with a configuration of ITO/NPB(50 nm)/Complex(50 nm)/Mg/Ag(10:1) were fabricated. Strong blue and green emission were observed from thin solid film and EL device of AlMq₂q′ and Alq₂q′, respectively. The results revealed that the PL and EL emission wavelengths of these materials are primarily determined by Mq and q (first ligand), whereas phenolato ligand (second ligand) has little effect on the emission wavelength but remarkable influence on EL efficiency.     

Influence of γ′ and grain boundary carbide on tensile fracture behaviors of Nimonic 263

Tensile fracture behaviors of Nimonic 263 after three different heat treatments have been investigated. Standard heat treatment produces 10% γ′ coupled with precipitate free zones (PFZs), and M₂₃C₆ carbide densely distributed at grain boundaries (GBs). Alternative heat treatment causes dense distribution of GB carbides and precipitation of 1–3% γ′ with the absence of PFZs. Solution-treated sample has neither γ′ nor M₂₃C₆ carbide. Room temperature tensile tests indicate both standard and alternative heat-treated samples show intergranular fracture, but the elongation of the latter is two times larger than that of the former. The combined effect of GB carbides and intensive slip bands accounts for the intergranular fracture. The γ′ volume fraction affects elongation. Solution-treated sample displays transgranular fracture mode. Lack of restriction to dislocation mobility in grains interior and the weak interaction between GBs and dislocations are responsible for the transgranular fracture. The effect of PFZs on fracture mode may be negligible.     

Synthesis of single nanocrystal phase γ′-Fe4N on NaCl substrate by DC magnetron sputtering

The single-phase γ′-Fe₄N nanocrystal magnetic films with grain size of d = 40–60 nm were synthesized on single crystal NaCl (1 0 0) substrate by DC magnetron sputtering at 150 °C. The structure, morphology of the single-phase γ′-Fe₄N films were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and the magnetic properties of samples prepared at different substrate temperatures were investigated by superconducting quantum interference device (SQUID). It is shown that substrate temperature has a significant influence on the crystalline structure and magnetic properties for Fe–N films. As substrate temperature was increased, the saturation magnetization for the deposited films increased, but the coercivity reduced.     

Retransformation (α′→γ) kinetics of strain induced martensite in 304 stainless steel

Coupons of austenitic 304 stainless steel (γ) were transformed to approximately 90% martensite (α′) and 10% austenite by rolling at 77 K. Subsequently the reverse α′→γ transformation was instigated by heating the coupons to 680°C. The retransformation was monitored, in situ, by dilatometry and neutron Bragg edge diffraction (BED). Results from the two techniques show good agreement and suggest that the transformation kinetics are best described by two Avrami exponents, n=2.5 and n=0.2 respectively. A limited discussion of the lattice parameter evolution during the transformation is included. Possible mechanisms for growth dynamics and stress relaxation are discussed.     

Anisotropy of Young's modulus and tensile properties in cold rolled α′ martensite Ti–V–Sn alloys

Young's modulus and tensile properties of cold rolled Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloy plates consisting of α′ martensite were investigated as a function of tensile axis orientation in this work. A single phase of α′ (hcp) martensite is obtained in Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloys by quenching after solution treatment. By 86% cold rolling, acicular α′ martensite microstructures change into extremely refined dislocation cell-like structure with an average size of 60 nm, accompanied with the development of cold rolling texture in which the basal plane normal is tilted from the plate normal direction (ND) toward transverse direction (TD) at angles of ±49° for Ti–8% V alloy and ±46° for (Ti–8 mass% V)–4 mass% Sn alloy. No apparent anisotropy of Young's modulus (E) is observed for as-quenched Ti–8% V (E = 76–83 GPa) and (Ti–8% V)-4%Sn (E = 69–79 GPa). In contrast, Young's modulus increases with increasing angle from the rolling direction (RD) to TD for cold rolled Ti–8% V (E = 72–94 GPa) and (Ti–8% V)–4%Sn (E = 63–85 GPa). The observed anisotropy of Young's modulus can be reasonably explained in terms of the cold rolling α′ texture.0.2% proof stress and tensile strength are independent of tensile orientation for cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys. In contrast, larger elongation to fracture is obtained in specimens deviated by 30°, 45° and 60° from RD than by 0°, 75° and 90°. Scanning electron microscopy (SEM) fractographs reveal that quasi-cleavage-like fracture plane appears in 0° specimen of cold rolled Ti–8% V which shows brittle fracture and other specimens of cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys are fractured accompanied with necking and dimple formation. It is suggested from these results that brittle fracture is related to the activation of limited number of slip system and Sn addition leads to the activation of multiple slip systems.     

Solute diffusion in the γ′ phase of Ni based alloys

We systematically investigate the diffusion mechanisms of 3d (Ti–Cu), 4d (Zr–Ag) and 5d (Hf–Au) transition metal solutes in γ′-Ni₃Al phase using first-principles calculations. The results reveal that the diffusion of Ni-substituting solute is mainly controlled by the sublattice diffusion mechanism via Ni vacancies and the diffusion of Al-substituting solute is mostly governed by the formation of the anti-structure defects on the Ni sublattice with negligible contribution of the anti-structure bridge mechanism. The elements which occupy both the Al and Ni sites show a diffusion behavior similar to that of the Ni-substituting solutes. Our calculations show that larger atoms can move much faster than smaller atoms, which disprove the traditional view that larger atoms move slower than smaller atoms.     

Structural, dielectric and electrical conducting properties of CsB′B′′O6 (B′=Nb, Ta; B′′=W, Mo) ceramics

Polycrystalline samples of the defect pyrochlore-type CsB′B′′O₆ (B′=Nb, Ta; B′′=W, Mo) compounds were prepared by solid-state reaction technique. The formation of the compounds was checked by X-ray diffraction (XRD) method. All the compounds were found to have a cubic crystal structure at room temperature. Dielectric studies of the tungstate compounds, CsNbWO₆ and CsTaWO₆ indicated a small dielectric anomaly at (183±2) and (328±2) K, respectively, whereas the molybdate compounds, CsNbMoO₆ and CsTaMoO₆ did not exhibit such anomaly. The conductivity measurements indicated ionic transports (t_ion≥0.80) in the high temperature region (≥573 K).     

Phase separation in PM 2000™ Fe-base ODS alloy: Experimental study at the atomic level

The coarsening of the three-dimensional microstructure resulting from phase separation during ageing at 748 K of a Fe-based PM 2000™ oxide dispersion strengthened (ODS) steel has been investigated by atom probe tomography and hardness measurements. Phase separation resulted in the formation of isolated particles of the chromium-enriched α′ phase. The aluminum and titanium were found to preferential partition to the iron-rich α phase. The partitioning of aluminum is consistent with theoretical calculations. The change in the scale of the chromium-enriched α′ phase was found to fit a power law with a time exponent of 0.32 in accordance with that predicted by the classical Lifshitz, Slyozov and Wagner (LSW) theory. The solute concentrations of the coexisting α and α′ phases were estimated from concentration frequency distributions with the Langer–Bar-on–Miller (LBM) method and proximity histograms. The hardness was linearly related to the chromium content of the α′ phase.     

Two-target DSAM following the (n,n′γ) reaction with fast reactor neutrons

A version of the Doppler-shift attenuation method (DSAM) is applied for the first time to measure lifetimes of nuclear states excited in the (n,n′γ) reaction with fast reactor neutrons simultaneously in two targets. The peculiarities of the procedure in connection both with the nature of the nuclear reaction used and with processing of the experimental data are described in detail.     

Synthesis and electroluminescence properties of zinc(2,2′ bipyridine)8-hydroxyquinoline

New electroluminescent material, namely zinc(2,2′ bipyridine)8-hydroxyquinoline [Zn(Bpy)q] has been synthesized and characterized. A solution of Zn(Bpy)q showed absorption maxima at 382 nm and 342 nm in toluene solution attributed to π − π transition. The photoluminescence spectrum in toluene solution showed peak at 545 nm. The material was stable up to 350 °C. Organic light emitting diode (OLED) fabricated with the structure ITO/α-NPD/Zn(Bpy)q/Alq₃/LiF/Al exhibits a broad electroluminescence peak at 548 nm. The maximum current efficiency of OLED was 1.34 cd/A at 5 V and the maximum power efficiency 0.84 lm/W at 5 V.     

Influence of applied stress on the γ′ directional coarsening in a single crystal superalloy

It was found in a commercial single crystal superalloy CMSX-4 that preferential orientation of the γ′ rafting in dendrite core was not dependent on the sign of the applied stress σ_A, but on the sign of the sum of the applied stress σ_A and a critical equivalent stress σ_c. This critical equivalent stress σ_c caused by material inhomogeneity has been predicted previously; however it was first determined experimentally to be in the range 39.8–47.2 MPa in the present study. Moreover, it qualitatively demonstrated that the critical equivalent stress σ_c played a significant role in the creep behavior of superalloys at high temperature and low stress.     

The photovoltaic effect in poly(p-phenylene-2,3′-bis(3,2′-diphenyl)-quinoxaline-7-7′-diyl)

We have investigated the photovoltaic properties of poly( p-phenylene-2,3′-bis(3,2′-diphenyl)-quinoxaline-7-7′-diyl) (PPQ) in sandwich structure devices. This polymer contains electron deficient quinoxaline moieties that are expected to give rise to a high electron affinity and to the possibility of good electron transport properties. The spectral response of the photocurrent shows qualitatively that the electron mobility is higher than the hole mobility in PPQ. The quantum efficiency of the short-circuit photocurrent is, however, small, namely only 1.7 × 10⁻⁵% under 10 mW illumination at 420 nm. Doping with tetra(1-dimethylamino-phenyl)-ethynylene (TDPE) increases the quantum efficiency of the short-circuit current to 4 × 10^-4%, probably due to enhanced exciton dissociation. Even with the TDPE dopant, the limiting factor for the photocurrent appears to be charge transport to the contacts.     

Electrical conductivity of metastable κ-CeZrO4 phase possessing ordered arrangement of Ce and Zr ions

Electrical conductivity σ_t of metastable κ-CeZrO₄ possessing ordered arrangement of Ce and Zr ions in a manner similar to a pyrochlore-type was measured as a function of temperature and time, and compared with tetragonal metastable t′-(Ce_0.5Zr_0.5)O₂ and t′_meta-(Ce_0.5Zr_0.5)O₂ phases possessing random arrangement of the cations. The κ disk was prepared by reoxidizing a pyrochlore-type precursor in O₂ gas at 873 K. The σ_t as measured for the κ-CeZrO₄ was reproducible as a function of temperatures between 957 and 1190 K. At increasing temperatures above 1233 K, the σ_t decreased gradually with time due to the phase transition: κ→t′, and became consistent with the t′. Although the κ-CeZrO₄ phase is thermodynamically less stable than the t′-(Ce_0.5Zr_0.5)O₂, it was virtually stable up to around 1233 K. It was found from the change in the σ_t due to the phase transition that the σ_t for the metastable κ-CeZrO₄ was an order of magnitude higher than that for the t′ and was similar to that for the t′_meta. It was previously reported that a phase transition, t′_meta→t′, occurred above 1143 K. The phase transition, κ→t′, accompanied by redistribution of the cations appeared to occur at higher temperatures than that for t′_meta→t′ leaving random cation arrangement.     

Visible to near-infrared organic light-emitting diodes using phosphorescent materials by solution process

The characteristics of visible to near-infrared OLEDs with co-doping three phosphorescent dyes, iridium (III) bis(2-(4,6-difluorephenyl)pyridinato-N,C²′) (FIrpic), tris(1-phenylisoquinoline)iridium(III) (Ir(piq)₃), Pt-tetraphenyltetrabenzoporphyrin (Pt(tpbp)) in poly(N-vinylcarbazole) host as blue, red and near-infrared emitters are investigated. Visible to near-infrared OLEDs covering the wavelength range from 450 to 850 nm were achieved. The device with 11.7 wt.% FIrpic, 0.3 wt.% Ir(piq)₃ and 0.1 wt.% Pt(tpbp) showed white light emission of CIE (0.34, 0.39). The co-doping results in efficient cascade energy transfer from host through Ir complexes. For 0.1 wt.% Pt(tpbp), the optimal device exhibited the maximum output power of 3 mW/cm², maximum luminance of 2900 cd/m² and the maximum efficiency of 7 cd/A.     

The inhibition of 4-(2′-amino-5′-methylphenylazo) antipyrine on corrosion of mild steel in HCl solution

The effect of 4-(2′-amino-5′-methylphenylazo) antipyrine (AMPA) on the corrosion of mild steel in a 2 M HCl solution was studied using weight loss and potentiodynamic polarization techniques. All of the data reveal that AMPA acts as an inhibitor in the acid environment; furthermore, polarization data show that the compound behaves as a mixed-type inhibitor. It was found that the inhibition efficiency increases with an increase in AMPA concentration but decreases with an increase in temperature. Flory–Huggins adsorption isotherm and El Awady thermodynamic–kinetic model fit the experimental data of the studied compound. Thermodynamic parameters for corrosion and adsorption processes were obtained from experimental data of the temperature studies.     

Photo-induced alignment behavior of azobenzene compound in thin film

Photo-induced molecular alignment behavior of spin-coated poly(4,4′-azobenzene pyromellitamic acid) (PAA(azo)) film was investigated by Fourier transform infrared spectroscopy measurement, atomic force microscope and transmission electron microscope observation. As-spun PAA(azo) flm was found to be smooth and uniform with an amorphous structure. Upon irradiation of linearly polarized ultraviolet light, the molecular ordering and crystallization were induced, and the film surface was roughened slightly. The PAA(azo) film converted to poly(4,4′-azobenzene pyromellitimide) (PI(azo)) film with higher ordering and crystallinity by subsequent thermal treatment. The PI(azo) film was useful as an active layer to introduce the molecular alignment of copper phthalocyanine (CuPc).     

Size effects of γ′ precipitate on the creep properties of directionally solidified nickel-base super-alloys at middle temperature

Nickel-base super-alloys consist of two phases named γ-phase of nickel matrix and γ′-phase of precipitates, which are dispersed uniformly in the matrix. The morphologies and sizes of γ′ precipitates have strong effects on the creep properties of the alloys. At the middle temperature (850 °C), the rafting effect of the precipitate is not obvious, and the size effects of precipitates are dominant. In this paper, a crystal plasticity constitutive model is developed, which considers damage and strain gradient to reflect the size effect of the creep property. This model is implemented into ABAQUS as an interface of user material (UMAT). Two different precipitate sizes are studied using a unit-cell model of alloys with the same volume fraction. By Comparison with the experiment data, the simulation results are reasonable to demonstrate the significant size effect of precipitates on the creep properties of nickel-base super-alloys, which indicates that the creep rates are lower and the rupture lives are longer when the precipitate sizes are smaller with constant fraction.     

New Functional Polymers and Materials Based on 2,2′:6′,2″‐Terpyridine Metal Complexes

New inorganic–organic hybrid structures based on metal complexes have become of increasing interest over the last few decades in the search for new materials. Many different polypyridyl metal complexes have been investigated. Recently, a strong increase in interest regarding 2,2′:6′,2″‐terpyridine has been observed. In particular, octahedral bis‐2,2′:6′,2″‐terpyridine metal complexes offer the advantages of increased symmetry and, in the case of ruthenium(III )/ruthenium(II ) complexation, an entrance to a directed complexation technique. Apart from the combination with polymeric systems, ordered inorganic–organic structures on surfaces are becoming better understood concurrently with the development of sophisticated nanotechnology characterization techniques. There are many ongoing efforts that include terpyridine complex structures, especially concerning photophysical processes such as solar light to energy conversion. This review deals with the incorporation of terpyridine complexes into polymeric structures such as poly(ethylene glycol), poly(styrene), dendrimers, biomacromolecules, micelles, and resins, as well as the combination of terpyridine complexes with surfaces for electrocatalytic, photophysical, and self‐assembly purposes.     

Occurrence, distribution and possible sources of organochlorine pesticides in agricultural soil of Shanghai, China

Surface soil samples from agricultural soil of Shanghai were collected and analyzed for 24 organochlorine pesticides (OCPs). The concentrations were in the ranges of nd–10.38 ng g⁻¹ for HCHs (sum of α-, β-, γ- and δ-HCH), 0.77–247.45 ng g⁻¹ for DDTs (sum of p,p′-DDT, p,p′-DDD, p,p′-DDE, and o,p′-DDT), 0.84–10.08 ng g⁻¹ for CHLs (sum of heptachlor, heptachlor epoxide, cis-chlordane, trans-chlordane, and trans-nonachlor), nd–3.68 ng g⁻¹ for endosulfan (sum of α- and β-endosulfan), 0.10–3.62 ng g⁻¹ for HCB and nd–5.69 ng g⁻¹ for other OCPs (sum of aldrin, dieldrin and endrin). The total OCPs concentrations ranged from 3.16 to 265.24 ng g⁻¹ and the main contaminated areas were distributed in the south regions of Shanghai (including Fengxian, Nanhui and Jinshan districts). According to the measured concentrations and detection frequencies, HCHs, DDTs, HCB and heptachlor epoxide were the most dominant compounds among the 24 OCPs. The different compositions of DDT, HCH, chlordane and endosulfan indicated that the residues of these compounds in most soil samples originated from historical application, besides slight recent introduction at some sampling locations. The correlation analysis showed no significant relationship between TOC and OCPs. The quality of Shanghai agricultural soil was classified as low pollution by OCPs.