Phase Equilibrium in the System Ln-Mn-O IV. Ln=Sm at 1100°C

Phase equilibrium in a Sm-Mn-O system has been established at 1100°C while changing the oxygen partial pressure from 0 to 13.00 in −log (P_O2/atm), and a phase diagram at 1100°C is presented for a Sm₂O₃-MnO-MnO₂ system. Under the experimental conditions, Sm₂O₃, MnO, Mn₃O₄, SmMnO₃, and SmMn₂O₅ phases are present at 1100°C, but Sm₂MnO₄, Mn₂O₃, and MnO₂ are unstable in the system. LnMn₂O₅- type phase is stable under the present experimental conditions differing from the previously reported La-Mn-O and Nd-Mn-O systems.A wide range of nonstoichiometry has been found in the SmMnO₃ phase which coexisted with Sm₂O₃. X ranges from −0.010 at log P_O2=−10.00 to 0.098 at log P_O2=0 in the molecular formula of SmMnO_3+X. The nonstoichiometry is represented by an equation, N_O/N_SmMnO3=3.00×10⁻⁴ (log P_O2)³ +6.20×10⁻³ (log P_O2)²+4.28×10⁻² (log P_O2)+0.0979, and the activities of the components in the solid solution are calculated using the equation. SmMnO₃ seems to vary in composition in the Sm₂O₃-rich or Sm₂O₃-poor side as it was with LaMnO₃. SmMn₂O₅ is slightly nonstoichiometric.Lattice constants of SmMnO₃ made under different oxygen partial pressures and those of SmMn₂O₅ prepared in air were determined, along with spacings and relative intensities of SmMn₂O₅. Standard Gibbs energies of reactions shown in the system were calculated and compared with previously reported values.     

Phase equilibrium in the system Ln-Mn-O: V. Ln=Yb and Dy at 1100°C

Phase equilibrium was established in the Yb-Mn-O and Dy-Mn-O systems at 1100°C by varying the oxygen partial pressure from −log (P_O2/atm)=0-13.00, allowing construction of phase diagrams at 1100°C for the systems Ln₂O₃-MnO-MnO₂. Under experimental conditions, Yb₂O₃, MnO, Mn₃O₄, and YbMnO₃ phases are found to be present in the Yb-Mn-O system, whereas Dy₂O₃, MnO, Mn₃O₄ DyMnO₃, and DyMn₂O₅ phases are present in the Dy-Mn-O system. Ln₂MnO₄, Mn₂O₃, and MnO₂ are not stable in either system. Small nonstoichiometric ranges are found in the LnMnO₃ phase, with the nonstoichiometry represented by the equations, N_O/N_YbMnO3=1.00×10⁻⁴(log P_O2)³+1.30×10⁻³(log P_O2)²+7.20×10⁻³(log P_O2)+5.00×10⁻⁵ and N_O/N_DyMnO3=1.00×10⁻⁴(log P_O2)³+1.80×10⁻³(log P_O2)²+9.30×10⁻³(log P_O2)+1.69×10⁻². Activities of the components in the solid solutions are calculated using these equations. LnMnO₃ may range Ln₂O₃-rich to Ln₂O₃-poor, while MnO is slightly nonstoichiometric to the oxygen-rich side. DyMn₂O₅ also seems to be nonstoichiometric. Lattice constants of LnMnO₃ under different oxygen partial pressures were determined, as well as lattice constants of DyMn₂O₅ quenched in air. The standard Gibbs energy changes of reactions appearing in the phase diagrams were calculated.     

Phase equilibrium in the system Y-Fe-O at 1100°C

Phase equilibrium was established in the Y-Fe-O system at 1100°C by varying the oxygen partial pressure from −log(P_O2/atm)=15.00 to 0, allowing construction of a phase diagram at 1100°C for the system Y₂O₃-Fe-Fe₂O₃. In the system, two ternary compounds, YFeO₃ and Y₃Fe₅O₁₂, were stable and had nonstoichiometric composition, whereas YFe₂O₄ was not found to be stable. The present result was different from that of previous studies at 1200°C, in which YFe₂O₄ was stable, along with the above two ternary compounds. Lattice constants of YFeO₃ and Y₃Fe₅O₁₂, prepared in air by a quenching method, were determined and compared with previous values, and showed close agreement. The standard Gibbs energy changes of the reactions in the Fe-O system, Fe+1/2O₂=FeO, 3FeO+1/2O₂=Fe₃O₄, and 2/3Fe₃O₄+1/6O₂=Fe₂O₃, were determined, and the obtained values were compared with the previous values. The standard Gibbs energy changes of the reactions, Fe+1/2Y₂O₃+3/4O₂=YFeO₃, and 3YFeO₃+2/3Fe₃O₄+1/6O₂=Y₃Fe₅O₁₂, were calculated from the oxygen partial pressures in equilibrium.     

Phase equilibrium in the system Ln-Mn-O VI: Ln=Ho and Tb at 1100°C

Phase equilibria were established in Ho-Mn-O and Tb-Mn-O systems at 1100°C by varying the oxygen partial pressure from −log(P_O2/atm)=0-13.00, and phase diagrams for the corresponding Ln₂O₃-MnO-MnO₂ systems at 1100°C were presented. Stable Ln₂O₃, MnO, Mn₃O₄, LnMnO₃, and LnMn₂O₅ phases were found at 1100°C, whereas Ln₂Mn₂O₇, Ln₂MnO₄, Mn₂O₃, and MnO₂ were not found to be stable. Small nonstoichiometric ranges were found in the LnMnO₃ phase, with the composition of LnMnO₃ represented as functions of log(P_O2/atm), and . Activities of the components in the solid solution were calculated from these equations. The composition of LnMnO₃ may range from Ln₂O₃ rich to Ln₂O₃ poor, while MnO is slightly nonstoichiometric, being oxygen rich and LnMn₂O₅ seems to be nonstoichiometric. Lattice constants of LnMnO₃ quenched at different oxygen partial pressures and of LnMn₂O₅ quenched in air were determined. The standard Gibbs energy changes of the reactions appearing in the phase diagrams were also calculated. The relationship between the tolerance factor of LnMnO₃ and ΔG⁰of reaction, (1/2)Ln₂O₃+MnO+(1/4)O₂=LnMnO₃, is shown graphically.     

Thermodynamic study of sodium-iron oxides: Part I. mass spectrometric study of Na-Fe oxides

Vaporization behavior of Na₄FeO₃(s) was thermodynamically studied from 590 to 717 K by means of high temperature mass spectrometry. It was found that Na₄FeO₃(s) decomposed into Na₃FeO₃(s) and released sodium vapor. The temperature dependence of partial vapor pressure of sodium over Na₄FeO₃(s) was measured so that the Gibbs energy of formation of Na₃FeO₃(s) was evaluated as Δ_fG°(Na₃FeO₃)=−1168629+338.34×T.     

Fundamentals and applications of needle trap devices: A critical review

The needle trap device (NTD) is an extraction trap that contains a sorbent inside a small needle, through which fluid can be actively drawn into and out of by a gas-tight syringe or pump, or analytes can be introduced passively to the trap by diffusion. The needle trap (NT) is a potentially solventless sampling technique/sample preparation and introduction device. Both fluid-borne analytes and particles can be trapped inside the needle and then adsorbed analytes are desorbed in an inlet of analytical instrument and introduced for identification and quantification. The fluid may be either gaseous or liquid. The objectives of this critical review are to summarize the theory of the sampling process for both active and passive time-average extraction modes in addition to outlining the evolution of the technology and main applications.     

Vapour–liquid equilibria,enthalpy of mixing of binary mixtures containing diisopropylether ‘DIPE’ and monoaromatic hydrocarbons: Experimental results and modelling

The experimental isothermal P–x–y data between 263.15 and 343.15 K at 10 K intervals of liquid binary mixtures 2,2′-oxybis[propane] (diisopropylether or DIPE) + toluene, +m-xylene and of the three pure components are reported. Data reduction by Barker's method provides correlation for excess molar Gibbs energy (G^E).     

Non-rigid molecules : III. Sigmatropism in organometalliic complexes of indene

The effects of π system geometry upon the transition states for sigmatropism in five-membered rings is discussed semi-quantitatively using the PMO theory. Comparison of the results with measured activation energies suggests that the [1, 3] averaging in organometallic indene complexes proceeds via sequential [1, 2] shifts in all those cases examined.     

Crystallization in ultra-thin polymer films: Morphogenesis and thermodynamical aspects

We present a computer model for polymer crystallization in ultra-thin films where chains are considered as dynamical units. In our model chains can change their internal state of order by cooperative motions to improve thermodynamic stability. The interplay between reorganization, enthalpic interactions and the morphology of crystals enables us to explain many properties of growth, morphogenesis and melting of polymer lamellae. We emphasize the relation between the thermodynamic stability of non-equilibrium crystals and morphological features which are beyond the average thickness of the lamellae. In particular, we show that melting of polymers is preceded by reorganization processes and the stability of polymer crystals is not necessarily related to the structure formed at the crystallization point. The simulations allow for the determination of some non-equilibrium properties such as the internal energy and the non-equilibrium heat capacity. We show that multiple-peak melting endotherms result from morphological transformations. The results of our computer simulations are compared with AFM observations in ultra-thin polyethyleneoxide films.     

New hydrofluoropolyethers: I. Synthesis and reaction pathway evaluation

A novel family of hydrofluoropolyethers (HFPEs) was obtained with 60-80% selectivity by hydrogenation of perfluoropolyether acyl chlorides with Pt/CaF₂. These compounds are characterized by a macromeric fluorinated body end-capped, on one or both sides, by a (1,1-difluoro)ethoxy group. A reaction pathway for the reduction was proposed consistently with the observed yields and side products. The hemiacetal originated by reaction of the aldehyde (first product of reduction) with the corresponding alcohol was postulated to be the key precursor leading to the HFPE. The metal appears to play a fundamental role promoting the hydrogenolysis of this unexpected intermediate. Exhaustive reduction of the alcohol, generally recognized as the path affording hydrocarbons in the hydrogenation of acyl chlorides, was excluded by products analysis and by specific experiments.     

Dual-wavelength spectrophotometry: Part III. Determination of arsenazo I in arsenazo III

A simple rapid spectrophotometric method for the determination of arsenazo I in the presence of large amounts or arsenazo III by means or a dual-wavelength method is discussed. By proper selection of the combination of two wavelengths, γ1 = 502.0 nm and γ2 = 575.3 nm, arsenazo III can be masked instrumentally even when its concentration varies. By this method about 0.5– 40%of arsenazo I in arscnazo III can be determined very easily and accurately.     

Massenspektroskopische fragmentierungsreaktionen—III : Das scheinbar anomale verhalten von 3-hydroxytetrahydropyransystemen

Tetrahydropyran derivatives may lose C-2 together with a substituent from C-3 accompanied by ring contraction. This explains why, e.g., compounds derived from 3-hydroxytetrahydropyran sometimes fragment in a manner expected for an isomeric tetrahydrofuran system. The prerequisities for this rearrangement and its mechanism are discussed.     

Quantitative millimetre wavelength spectrometry at pressures approaching atmospheric: II. Determination of oxygen at atmospheric pressure

A millimetre wavelength (MMW) Fabry-Perot cavity spectrometer described in earlier work has been applied to the measurement of oxygen absorption at 60 GHz and atmospheric pressure in a gas matrix of nitrogen. The spectrometer has also been modified such that the MMW source is stabilised by a sub-harmonic microwave signal transmitted by an infrared carrier on a single mode telecommunications fibre optic. This is a step towards developing an instrument comprising minimal electronic components that can perform MMW spectrometry remotely. Oxygen determinations were achieved by monitoring the change in the quality factor (Q) of a resonant Fabry-Perot cavity due to the presence of an absorbing sample. The MMW absorption of the sample was determined by incrementing the frequency modulation (FM) deviation of the source frequency scanning the cavity resonance profile. The response curve of absorption signal versus fraction of oxygen in nitrogen was found to be linear throughout the working range of 1-100% O₂ (v/v) in N₂ with a slope of (1.407±0.007)×10⁻⁴ m⁻¹ (% O₂)⁻¹. The detection limit (3× standard deviation of the background) was found to be ∼0.8% (v/v). The MMW technique employed is advantageous since, unlike common MMW techniques, there is no vacuum requirement. Application of this method, to the monitoring of oxygen in gas mixtures of practical importance, is proposed. Values of the oxygen spectral absorption coefficients of lines between 55 and 60 GHz were measured at reduced pressure and found to be within ±2% of previous literature values. A pressure correction coefficient for O₂ absorption at 60 GHz in the 45-121 kPa range was obtained and found to be (1.354±0.014)×10⁻⁴ m⁻¹ kPa⁻¹.     

Analysis of polyethoxylated surfactants in microemulsion-oil-water systems: Part II

Commercial ethoxylated surfactants are always a mixture of oligomers with different ethylene oxide number (EON). The different oligomers were separated by high performance liquid chromatography (HPLC) on an amino column using a mixture of polar and nonpolar mobile phases. Surfactant oil-water-systems were studied according to the unidimensional scan technique. The surfactant content in the oil, microemulsion and water phases was determined by UV spectroscopy and HPLC. The partitioning of the surfactant oligomers in the oil and water phases of a Winsor III system was determined. The effect of different salts on the surfactant partitioning is discussed.     

Fluorinated-plasma coating on polyhydroxyalcanoate PHBV: Effect on the biodegradation

Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) was covered with an hydrophobic layer from plasma polymerization of tetradecafluorohexane, octadecafluorooctane, 3,3,4,4,5,5,6,6,6-nonafluoro-hex-1-ene and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-oct-1-ene. The water contact angle increased from 74° for untreated films to 98° for the treated films and the surface energy decreased from 40.9 to 18.8 mJ m⁻². XPS analysis showed the introduction of 54% fluorine and 3-7% oxygen, the binding energies were assigned to chemically differently bonded carbon atoms. CF₂/CF₃ molar ratio in plasma layers was lower than that in the monomers due to molecular fragmentation, however the extent of monomer structure retention in PFH, PFO saturated chains is higher than in NFH, TDFO unsaturated chains. Biodegradation tests under aerobic conditions showed that the fluorinated plasma layer inhibited the biodegradation of the PHBV film underneath.     

Protonation of metal carbonyl complexes : III. Cyclopentadienyl carbonyl complexes of manganese

Using IR spectroscopy, the phosphine derivatives of cyclopentadienylmanganese tricarbonyl have been shown to undergo protonation in solutions of trifluoroacetic acid and in mixtures of this solvent with methylene chloride, protonation at the metal atom being the most probable. Ease of protonation increases with increasing electron-releasing properties of both the π-ring substituents and the phosphine ligands attached to the manganese atom.     

High pressure phase equilibria in methane + waxy systems: 1. Methane + heptadecane

Fluid–fluid and fluid–solid phase equilibrium were experimentally determined under pressure on the system methane + heptadecane using a full visibility cell. Measurements were performed using the synthetic method on mixtures ranging from pure heptadecane to 99% of methane. The liquid–solid phase transitions were investigated up to 90 MPa and fluid phase boundary was studied in the temperature domain from 293 to 373 K. The appearance of a minimum in the three phase (V–L–S) equilibrium curve is discussed and it is shown that the difference in the solid phase structure and the presence of a solid–solid phase transition do not affect significantly the phase diagram determined.     

Steric effects in conjugated systems: II. 2,3-Dimethylbutadiene

Based on earlier results of conformational analysis by the Wiberg method¹ of monosubstituted methylbutadienes, analogous calculations for 2,3-dimethylbutadiene have been carried out. Contrary to the opinion of Aten et al.² who assumed almost free rotation, the molecule was shown to exhibit a considerable strain which hinders the rotation of methyl groups and lengthens the C_sp²-C_sp² bond compared with the length of the central bond in butadiene. The calculated lengthening agrees qualitatively with that obtained by electron diffraction¹.