Determination of vapour pressure and standard enthalpies of sublimation and vapourisation of N,N′-ethylenebis(2,4-pentanedion-iminoato)nickel(II) by a TG-based transpiration method

In order to identify a volatile metallo-organic precursor for the deposition of nickel films for CVD applications, equilibrium vapour pressure (p_e) measurements were carried out on a N,N′-ethylenebis(2,4-pentanedion-iminoato)nickel(II) (Ni[(acac)₂en]) by employing a TG-based transpiration method over the range 406 to 495 K leading to values of 118.0±4.1 and 83.3±3.8 kJ mol⁻¹ for the standard enthalpies of sublimation and vapourisation, respectively of Ni[(acac)₂en]. From the plot of log p_e against 1/T, the melting point was derived to be 463 K, which is in reasonable agreement with 469±3 K reported in the literature and was also observed in DTA and melting point studies.     

Determination of δ(18)O and δ(15)N in Nitrate

The analyses of both O and N isotopic compositions of nitrate have many potential applications in studies of nitrate sources and reactions in hydrology, oceanography, and atmospheric chemistry, but simple and precise methods for these analyses have yet to be developed. Testing of a new method involving reaction of potassium nitrate with catalyzed graphite (C + Pd + Au) at 520 °C resulted in quantitative recovery of N and O from nitrate as free CO(2), K(2)CO(3), and N(2). The δ(18)O values of nitrate reference materials were obtained by analyzing both the CO(2) and K(2)CO(3) from catalyzed graphite combustion. Provisional values of δ(18)O(VSMOW) for the internationally distributed KNO(3) reference materials IAEA-N3 and USGS-32 were both equal to +22.7 ± 0.5‰. Because the fraction of free CO(2) and the isotopic fractionation factor between CO(2) and K(2)CO(3) were constant in the combustion products, the δ(18)O value of KNO(3) could be calculated from measurements of the δ(18)O of free CO(2). Thus, δ(18)O(KNO)((3)) = aδ(18)O(free)(?)(CO)((2)) - b, where a and b were equal to 0.9967 and 3.3, respectively, for the specific conditions of the experiments. The catalyzed graphite combustion method can be used to determine δ(18)O of KNO(3) from measurements of δ(18)O of free CO(2) with reproducibility on the order of ±0.2‰ or better if local reference materials are prepared and analyzed with the samples. Reproducibility of δ(15)N was ±0.1‰ after trace amounts of CO were removed.     

TG/DTA-based techniques for the determination of equilibrium vapour pressures of N,N′-propylenebis(2,4-pentanedion-iminoato)nickel(II) for CVD applications

The Schiff’s base complexes of nickel(II) prepared by condensing 1,2-diaminopropane (pn), 1,3-diaminopropane (trien), 1,4-diaminobutane (tren) or 1,2-diaminobenzene (opdn) with 2,4-pentanedione (acac) in a 1:2 mole ratio followed by chelation with nickel(II) were examined for their volatility/decomposition behaviour for CVD applications. Among the complexes screened, only one complex namely N,N′-propylenebis (2,4-pentanedion-iminoato) nickel(II) (designated as [Ni(acac)₂pn], Ni′) exhibited a single stepped volatilisation commencing from above its melting point (T_o) of 431.9 K and ending up with nil residue at about 570 K. Fast Atom Bombardment Mass Spectrometry was employed to determine the molecular mass of the vapour species to be 295 in accordance with the molecular mass for the monomeric Ni(C₁₃H₂₀O₂N₂). The equilibrium vapour pressure (p_e) of Ni′ over the range of 434–498 K was determined to be log p_e/Pa = 13.771 (±0.574)–4925.4 (±258.2) K/T by employing a TG-based transpiration technique, which yielded a value of 94.3±5.0 kJ mol⁻¹ for its standard enthalpy of vapourisation . The DTA-based melting point depression (T_o–T) studies were carried out on four mixtures of Ni′ (as a volatile solvent) with bis(2,4-pentanedionato)nickel(II) (designated as Ni(acac)₂ or Ni″) as the non-volatile solute. The dependence of log X_Ni′ against 1/T(K) for the four mixtures with the solvent mole fraction X_Ni′ = 0.910, 0.897, 0.881 or 0.849 exhibited near constant slope leading to an average value of 19.4±1.6 kJ mol⁻¹ for the standard enthalpy of fusion . Combining and , a value of 113.7 ± 6.6 kJ mol⁻¹ for standard enthalpy of sublimation was derived to facilitate the estimation of vapour pressures for solid/vapour equilibrium below the melting point.     

Potentiometric studies of N,N′-Bis(2-dimethylaminoethyl)-N,N′-dimethyl-9,10 anthracenedimethanamine as a chemical sensing material for Zn(II) ions

A liquid membrane based Zn²⁺ ion selective electrode containing N,N′-Bis(2-dimethylaminoethyl)-N,N′-dimethyl-9,10 anthracenedimethanamine (Bis(TMEDA) anthracene) (I) as ionophore has been prepared and characterized. The membrane comprises of PVC, ionophore and plasticizer in the ratio of 33:2:65, respectively. It showed the best response in terms of detection limit (1.5 × 10^− 6 M) and working concentration range (1.0 × 10^− 5 M to 1.0 × 10^− 1 M) with Nernstian response towards Zn²⁺ ions. The electrode responds within 15 s of coming in contact with the solution. The potential response remains almost unchanged over a pH range of 3.0 to 7.5. The electrode can be used for at least 3 months without any considerable alteration in its response behavior. The proposed electrode revealed good selectivity towards Zn²⁺ ions over a number of alkali, alkaline earth, transition metals and some other heavy metal ions. The electrode has been used as an indicator electrode in the potentiometric titration of Zn²⁺ with EDTA. The proposed electrode also detected Zn²⁺ ions from real life samples.     

Experimental investigation of the self- and N(2)-broadened continuum within the ν(2) band of water vapor

We present an experimental study of the self- and N(2)-broadened H(2) O continuum in microwindows within the ν(2) fundamental centered at ~1600 cm(-1). The continuum is derived from transmission spectra recorded at room temperature with a BOMEM Fourier transform spectrometer at a resolution of ~0.040 cm(-1). Although we find general agreement with previous studies, our results suggest that there is significant near-wing super-Lorentzian behavior that produces a highly wave-number-dependent structure in the continuum as it is currently defined.     

Erosion of Vacuum-Arc Ti–N Coatings

We studied the fracture of vacuum-arc Ti–N coatings, produced under a nitrogen pressure (P _TiN) from 1 to 10³ mPa, after their bombardment with polyenergetic deuterium ions and the action of cavitation in tap water on them without ion irradiation. We showed that, in the case of action of cavitation on nonirradiated specimens of the coatings, their erosion rate can be evaluated from the relation V _c = C/(W ^0.75 H ^0.5). It was established that, after ion bombardment, the erosion rate under conditions of cavitation decreases by a factor of 1.5 for coatings where P _TiN > 100 mPa and increases by more than 30 times for P _TiN < 20 mPa as compared with nonirradiated specimens. The results obtained were analyzed using the phase diagram of the titanium-nitrogen system.     

Synthesis and characterization of new optically active poly(amide-imide)s derived from N,N′-(pyromellitoyl) bis-L-tyrosine and various diamines

Five new optically active poly(amide-imide)s(PAIs) 5a–e were prepared by direct polycondensation reaction of N,N′- (pyromellitoyl) bis-L-tyrosine 3 as chiral dicarboxylic acid with various aromatic diamines 4a–e. Triphenylphosphite(TPP)/pyridine(py) in the presence of calcium chloride (CaCl₂) and N-methyl-2-pyrrolidone (NMP) were successfully applied to direct polycondensation reaction. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.48 dL/g and 0.6 dL/g. They were analyzed with a C.H.N. elemental analyzer, FTIR, ¹H-NMR, UV-VIS spectroscopy and polarimeter (specific rotation measurement, [α] _D ²⁵ ). Thermogravimetric analysis (TGA) indicated that the residual weight percentage of polymers at 600 °C were between 48.66 % and 64.21 %, which showed their thermal stability. These polymers are attractive to be used as packing materials in chromatography columns for separation of enantiomers.     

Analysis of Si3N4+β-Si3N4 whisker ceramics

Dense Si₃N₄+-Si₃N₄ whisker composite ceramics were fabricated by hot pressing powder-whisker mixtures. Addition of -Si₃N₄ whiskers had no significant influence on the densification behaviour for up to 20 wt% addition. Light microscopy and scanning and transmission electron microscopy were used to study their microstructure and fracture behaviour. An increase in fracture toughness was observed for -Si₃N₄ whisker additions of up to 10 %. The main toughening mechanisms observed were crack deflection, crack branching, whisker-matrix debonding and whisker pull-out.     

Scatter Analysis of Fatigue Life and Prediction of S–N Curve

In this study, the effects of salt solution, the presence of notch on fatigue life scatter, and sample size selection for estimation of fatigue life under different probabilities and confidence levels have been investigated. Comparison has been made with smooth specimen tested in air medium. It is seen that notches have significantly higher effect than other factors (salt solutions, smooth geometry, etc.). The minimum number of specimens required for fatigue life estimation within tolerable error, R _o, at different fatigue testing conditions has also been presented both for log normal and Weibull distribution models. It has been found that estimation of fatigue life using Weibull model needs higher sample size than log normal model. Beyond a certain sample size, fatigue life estimation is independent of sample size. The article also presents a method for minimum sample size selection procedure to estimate fatigue life or to draw S?CN curve.     

Effect of grain size distribution on the strength of porous Si3N4 ceramics composed of elongated β-Si3N4 grains

The grain size distributions (diameter and aspect ratio) of porous Si₃N₄ ceramics composed of elongated -Si₃N₄ grains were evaluated statistically, and their effect on the pore size distribution and the flexural strength of the porous Si₃N₄ was investigated. Porous Si₃N₄ ceramics having porosities of 27 to 43% and median pore diameters of 0.56 to 0.96 m were used as specimens. The grain diameter distribution was well correlated to the pore size distribution of the porous Si₃N₄ ceramics. We concluded that the strength of the porous Si₃N₄ ceramics increased with increasing grain length of -Si₃N₄ as well as with decreasing porosity.     

Magnetic torque ofκ-(BEDT-TTF)2Cu[N(CN)2]Br single crystal

Magnetic torque of the single crystal of a layered superconductor -(BEDT-TTF)₂Cu[N(CN)₂]Br has been measured as a function of field direction with respect to the b-axis under several magnetic fields H up to 8 kOe in the temperature range from 1.5 to 20 K. Smaller value of the anisotropy parameter = 180 is obtained for Cu[N(CN)₂]Br salt than our previous report = 350 for -(BEDT-TTF)₂Cu(NCS)₂. The irreversible region in H — T phase diagram for Cu[N(CN)₂]Br salt with smaller is larger than that for Cu(NCS)₂ salt. A sharp cusp due to the intrinsic pinning is found near Hac-plane as in the case of our previous report on other layered superconductors.     

Inhibition of corrosion of mild steel in acid media by N′-benzylidene-3-(quinolin-4-ylthio)propanohydrazide

In the present investigation a new corrosion inhibitor, N′-(3,4-dihydroxybenzylidene)-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(DHBTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H₂SO₄ (0·5 M, 1 M) solutions using weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency measured by all the above three techniques were in good agreement with each other. The results showed that DHBTPH is a very good inhibitor for mild steel in acidic media. The inhibition efficiency in different acid media was found to be in the decreasing order 0·5 M H₂SO₄ > 1 M HCl > 1 M H₂SO₄ > 2 M HCl. The inhibition efficiency increases with increasing inhibitor concentration and with increasing temperature. It acts as an anodic inhibitor. Thermodynamic and activation parameters are discussed. Adsorption of DHBTPH was found to follow the Langmuir’s adsorption isotherm. Chemisorption mechanism is proposed. The mild steel samples were also analysed by scanning electron microscopy (SEM).     

Strain-induced precipitation kinetics of Nb(C,N) and precipitates evolution in austenite of Nb–Ti micro-alloyed steels

In this article, the precipitation–temperature–time (PTT) curves were obtained by plotting 1/A _r-time curves (A _r represents the area under the flow curves, and some details were clarified in the section “1/A _r method”) using two-stage interrupted compression testing. Based on the measured PTT curves, the L_J model has been applied to calculate the complete PTT curves by adjusting the modification factor, f, to be 0.022, from which it can be seen that they are both typical C-shaped with the nose temperature ranging from 900 to 925 °C. By using additivity rule, the continuous-cooling-precipitation (CCP) curves were established. And the critical cooling rates for precipitation start were also determined for different cooling start temperatures, and the effects of cooling rates and cooling start temperatures on CCP curves were systematically clarified. The evolution of precipitates was found to be in good agreement with PTT curves. Numerous fine and round precipitates were formed during holding after first compression deformation, which could have hindered static recrystallization kinetics and accounted for the plateaus on 1/A _r-time curves. In addition, The cubic precipitates are mainly undissoloved TiN-rich (Ti,Nb) (C,N) carbonitrides. And based on the CCP and continuous-cooling-transformation curves of tested steel, the effect of cooling paths on precipitation and transformation were also discussed in details.     

N×N阵列波导光栅(AWG)复用/解复用器

N×N阵列波导光栅(AWG)复用/解复用器     

A simple and effective synthesis of cadmium selenide in aqueous N,N′-dimethylformamide

Cadmium selenide has been synthesized directly from cadmium chloride in aqueous N,N′-dimethylformamide (DMF) by the use of cycloocteno-1,2,3-selenadiazole or the element itself as the source of selenium. The dark brown powders that are the end-products of these reactions were characterized by reflectance spectroscopy, powder X-ray diffraction and scanning electron microscopy.     

Synthesis and characterization of lanthanide(III) complexes with a mesogenic Schiff-base,N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine

A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine, H₂ddsdp (abbreviated as H₂L³) that exhibits nematic mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H₂L³, upon condensation with hydrated lanthanide(III) nitrates, yields Ln^III complexes of the general composition [Ln₂(L³H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. Among the metal complexes, only that of Ho^III is found to be mesogenic with smectic-X and nematic phases. The IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L³H₂) to the Ln^III ions through two phenolate oxygens, rendering the overall geometry of the complexes to seven-coordinated polyhedron, possibly distorted mono-capped octahedron.     

Neutral N,N′-bis(2-pyridinecarboxamide)-1,2-ethane as sensing material for determination of lutetium(III) ions in biological and environmental samples

The biological properties of the lutetium as well as other lanthanide ions, primarily based on their similarity to calcium, have been the bases for research into potential therapeutic applications of lanthanide series since the early part of the twentieth century. In this research, a Lu(III) potentiometric membrane sensor based on N,N′-bis(2-pyridinecarboxamide)-1,2-ethane (PCAE) is described. The sensor exhibits a Nernstian response over a concentration range of 1.0 × 10^? 6 mol L^? 1–1.0 × 10^? 1 mol L^? 1, with a detection limit of 6.0 × 10^? 7 mol L^? 1. The best performance was achieved with a membrane composition, consisting of 30% PVC, 63% o-nitrophenyl octyl ether (NPOE), 5% PCAE and 2% sodium tetraphenylborate (NaTPB). It was found that at the pH range of 4.0–9.0, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presents satisfactory reproducibility, very fast response time (5 s) and relatively good discriminating ability for Lu(III) ions with respect to many common cations and other lanthanide ions. The sensor has been applied to the determination of Lu(III) in human serum and in some soil samples where domestic devices were stored.     

Mixtures of (N2)1−x : (O2) x at High Pressures and Low Temperatures

We performed Raman measurements at 18 K and pressures up to 25 GPa in order to construct a tentative phase diagram of the (N ₂)_1–x :(O ₂)_x –system at low temperatures. We varied the composition of the mixed system over the whole concentration range. Here we focused on the systems with high nitrogen concentration and pressures above 2 GPa. It is known that at room temperature oxygen is highly solvable in the –phase of N ₂. The experimental results show that oxygen suppresses the disorder–order transition –N ₂.     

Synthesis of carboxylate derivatives of molybdenum and tungsten based on joint insertion of CO2 and PhNCS or N, N′-dicyclohexylcarbodiimide into M-Cl bonds

Reactions of the higher molybdenum and tungsten chlorides with phenyl isothiocyanate or with N, N′-dicyclohexylcarbodiimide and carbon dioxide in dichloroethane are the first to demonstrate the possibility of insertion of carbon dioxide in combination with other heterocumulenes into transition metal-halogen bonds. IR spectroscopy and elemental analysis data show that the reactions result in the attachment of the ligands at the same metal-chlorine bond and the formation of heteromolecular insertion products with the compositions $$\left[ {MoOCl_3 \left\{ {N\left( {Ph} \right)C\left( S \right)} \right\}_2 Nc\left( {Me} \right)Cl} \right]$$ and $$MCl_x \left\{ {OC\left( O \right)\left[ {\left( {Hex} \right)NCN\left( {Hex} \right)} \right]_2 } \right\}Cl,$$ where x = 4 and 5 for the Mo and W derivatives, respectively.