High Accuracy and High Sensitivity Measurements of the Electrooptic Effect in Undoped and MgO-Doped LiNbO3 Crystals

Accurate measurements of the composite electrooptic (EO) coefficients r_c consisting of the EO coefficients r₁₃, r₃₃, and the piezoelectric constant d₃₁ in undoped and MgO-doped LiNbO₃ (LN) were made by extracting the fundamental and third harmonic components from photo-detection signals of the parallel Nicol optics including the LN crystal driven by minimal sinusoidal voltage. The analysis of relationship between multiple-reflection rays in the EO crystal and the accuracy of measurement indicates that anti-reflection films must be coated on the end faces of the crystal for highly accurate measurements. Measured values of r_c of undoped and MgO-doped LN crystals at a wavelength of 632.8 nm were 19.8 ± 0.1 pm/V and 19.2 ± 0.1 pm/V, respectively.     

Investigation of the polyetherketone guest–host DR1/PEK-c polymer films by real-time monitoring of the second-harmonic generation

The real-time monitoring of the second-harmonic generation (SHG) was used to optimize the poling condition and to study the nonlinear optical (NLO) properties of the polyetherketone (PEK-c) guest–host polymer films. The high second-order NLO coefficient χ₃₃⁽²⁾=11.02 pm/v measured at 1.064 μm was achieved when the weight percent of DR1 guest in the polymer system is 20%. The NLO activity of the poled DR1/PEK-c polymer film can maintain more than 80% of its initial value when temperature is under 100°C, and the normalized second-order NLO coefficient can maintain more than 85% after 2400 s at 80°C.     

Surface Effect of Two Different Calcium Fluoride Fillers on the Non-Isothermal Crystallization Behavior of Poly(ethylene Terephthalate)

Two different types of calcium fluoride (CaF₂) particles were incorporated into a poly(ethylene terephthalate) (PET) matrix, fine particles (～350 nm), and nanoparticles (～70 nm). Both of them were synthesized by a chemical precipitation method using triethanolamine (TEA) as stabilizer. To obtain the nanoparticles, a greater amount of TEA was added during the synthesis in order to limit their growth. Therefore, unlike the fine particles, nanoparticles contained a greater amount of the stabilizer. Once CaF₂ particles were obtained, the composite materials were prepared by melt-blending PET and particles at different filler loadings. The influence of both kinds of particles on the non-isothermal crystallization behavior of PET was investigated by using differential scanning calorimetry and field emission scanning electron microscopy. The Jeziorny-modified Avrami equation was applied to describe the kinetics of the non-isothermal crystallization, and several parameters were analyzed (half-crystallization time, Avrami exponent, and rate constant). According to the results, it is clear that CaF₂ particles act as nucleating agents, accelerating the crystallization rate of PET. However, the effect on the crystallization rate was more noticeable with the addition of the fine particles where the surface plays an important role for epitaxial crystallization, while the addition of the nanoparticles with an organic surface coating resulted in a crystallization behavior similar to the observed for PET.     

A new method for measuring electro-optical coefficients of the optically active crystals

A new method has been proposed to measure the electro-optical coefficients of the crystals which have optical activity. By using this method, the half-wave voltage and the electro-optical coefficients of the optically active crystals La₃Ga₅SiO₁₄ (LGS), La₃Ga_5..5Nb_0.5O₁₄ (LGN), La₃Ga_5.5Ta_0.5Si₁₄ (LGT) have been determined. The resultants obtained are: γ₁₁(LGS)=1.9 pm/V, γ₁₁(LGN)=0.75 pm/V, γ₁₁(LGT)=0.57 pm/V. This method can also be used to simulate the on–off state of the electro-optical Q switch in the laser cavity, whether the switch is made of the ordinary crystals or the optically active crystals.     

Line broadening,shifting and mixing parameters for the ν1 + ν3 band of OCS perturbed by N2 and O2

In this paper, we report measured Rosenkranz N₂- and O₂-broadening, induced pressure-shift and mixing coefficients for OCS in the ν₁ + ν₃ band, using a multi-pressure fitting technique applied to the measured shapes of the lines, including the interference effects caused by the line overlaps. These measurements were made by analysing six laboratory absorption spectra recorded at 0.004 cm^?1 resolution using the Fourier transform spectrometer Bruker IFS125HR located at the Laboratoire Interuniversitaire des Systèmes Atmosphériques, in Créteil. The spectra have been recorded in the 1850–3000 cm^?1 wave number range at 295 K, using a multipass absorption cell with an optical path of 3.249 m. The total sample pressures ranged from 5.97 to 83.28 Torr with OCS volume mixing ratios between 0.001 and 0.013 in nitrogen or oxygen. We have been able to determine the N₂- and O₂-pressure-broadening coefficients of 81 ν₁ + ν₃ transitions with rotational quantum number J up to 50. The measured N₂- and O₂-broadening coefficients range from 0.0815 ± 0.0698 to 0.1169 ± 0.1027 cm^?1 atm^?1 at 295 K, respectively. Most of the measured pressure shifts are positive. The reported N₂- and O₂-induced pressure-shift coefficients vary from about ?0.0103 ± 0.0092 to 0.0097 ± 0.0092 cm^?1 atm^?1, respectively. We have examined the dependence of the measured broadening parameters on the quantum number m (m = ?J for the P branch and m = J + 1 for the R branch) and also developed an empirical expression to describe the broadening coefficients in terms of |m|. On average, this empirical expression reproduces the measured broadening coefficients to within 2%. Using a semi-classical Robert and Bonamy formalism, the theoretical broadening coefficients have been calculated at room temperature and compared with the experimental results. The theoretical results of the broadening coefficients are in very good overall agreement with the experimental data (2%).     

Fluorescence Chemosensor for Determination of Carbon Dioxide and Its Application for Biodegradation Analysis of Polymers

A novel fluorescence sensor has been developed and applied for the determination of carbon dioxide released from the biodegradation of polymer materials and for the evaluation of the biodegradability of polymers. The proposed analytical method is based on the extraordinarily quenching effect of carbonate on fluorescence signal of N,N-diphenylthiourea system. Under the optimized experimental conditions, the fluorescence quenching system performed satisfactorily in a linear detection concentration ranging from 2.00 × 10^?4 to 9.00 × 10^?3 mol L^?1 of carbonate. The detection limit is 8.33 × 10^?5 mol L^?1 for carbonate. This proposed fluorescence system for the selective sensing of carbonate has been successfully applied to determine the biodegradability of polybutylene succinate and related polymers under controlled composting environment with devices assembled in our laboratory. The results exhibited that the biodegradation rate and final biodegradation percentage of biodegradable thermoplastic poly(ester urethane) elastomers, which embodies the block copolymer of poly(butylene succinate) with poly(diethylene glycol succinate), were correlated to the amount of poly(diethylene glycol succinate). In addition, the maximum biodegradation percentage of the testing polymers has reached 45.01%. This research demonstrates the development of chemosensors for rapid, selective, and sensitive detection of carbon dioxide is important and significant for both environmental and biological science.     

PEO electrolytes containing dioctyl phthalate (DOP) for dye-sensitized nanocrystalline TiO2 solar cells

In this paper, we aim to prepare polymer electrolytes consisting of NaI and I₂ dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared spectra shifted to a lower wave number (Δf = 93 cm⁻¹), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and structural changes of PEO/NaI/I₂/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10^–4 S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P _max/P _in × 100) at one sun condition (100 mW/cm²). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO₂ layers were verified by field-emission scanning electron microscopy.     

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Mexiletine

The 60 MHz ¹H NMR spectra of mexiletine, 1-(2,6-dimethylphenoxy)-2-propanamine, 1, have been studied at 28° in CDCl₃ solution with the achiral reagent, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), 2, Eu(FOD)₃, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)-d-camphorato]europium(III), 3, Eu(FACAM)₃, and tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium(III), 4, Eu(HFC)₃. Substantial lanthanide-induced shifts were seen for the proton signals of 1 with each reagent. Appreciable enantiomeric shift differences were seen for both methyl signals and for each of the CH₂CH proton signals using 3 and 4 that should permit direct determinations of enantiomeric excess for samples of 1. A predominant conformation for 1 is suggested based on observed splittings of the CH₂ proton signals and their relative lanthanide-induced shifts.     

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Methastyridone, 2,2-Dimethyl-5-(2-Phenylethenyl)-4-Oxazolidinone

Abstract

The 60 MHz ¹H NMR spectra of methastyridone, 2,2-dimethyl-5-(2-phenylethenyl)-4-oxazolidinone, 1, have been studied at 28° in CDCl₃ solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, Eu(FOD)₃, and the chiral reagent tris[3-(heptafluoropropylhydroxy-methylene)-d?camphorato]europium(III), 3, Eu(HFC)₃.     

A new high-pressure polymorph of Ti2O3: implication for high-pressure phase transition in sesquioxides

The post-corundum phase transition has been investigated in Ti₂O₃ on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti₂O₃ was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti₂O₃ can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) Å, b=2.8009 (9) Å, c=7.9300 (23) Å, V=170.95 (15) Å³ at 19 GPa, and a=7.8240 (2) Å, b=2.8502 (1) Å, c=8.1209 (3) Å, V=181.10 (1) Å³ at ambient conditions. The Birch–Murnaghan equation of state yields K ₀=206 (3) GPa and K′₀=4 (fixed) for corundum phase, and K ₀=296 (4) GPa and K′₀=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti₂O₃ can be identified as Th₂S₃-type rather than U₂S₃-type structure. The transition from corundum-type to Th₂S₃-type structure accompanies the drastic change of the form of polyhedron: from TiO₆ octahedron in the corundum-type to TiO₇ polyhedron in the Th₂S₃-type structures.     

Molecular dynamics simulation of gas diffusion behavior in polyethylene terephthalate/aluminium/polyethylene interface

Molecular dynamics (MD) simulations were performed to estimate the diffusion coefficients of O₂ and H₂O molecules in polyethylene terephthalate/aluminum/polyethylene interface at the temperature of 298 K. It came out that the diffusion coefficient of gasses in the interface is smaller than that of a single polymer, and the diffusion coefficients compare well with experimental data as well as previously published work. Furthermore, the diffusion coefficients of H₂O molecules in the interface are preferable to that of O₂ molecules. Interestingly, the largest diffusion coefficient was detected in the polyethylene terephthalate/aluminum(1 0 0)/polyethylene interface, while the smallest value of the diffusion coefficients was found in the polyethylene terephthalate/aluminum(1 1 1)/polyethylene interface. Calculation and analysis of the interaction between aluminum and polymers indicated that the interaction of polymer/aluminum(1 1 0) has the most interface strength, and crystal density of the metal surface has a definite effect on the planar interface energy. What’s more, the figure of gas molecule concentration is further resulted that the interface make contribution to adsorption of gas molecules. Moreover, the diffusion is belonging to the Einstein diffusion in the multilayer materials, and this work provides some key clues to improve the performance of polymer materials.     

Theoretical investigation on kinetics and thermochemistry of reaction of CHF2CF2OCH2CF3 with OH radicals and global warming potentials

Theoretical investigation has been carried out on the mechanism, kinetics and thermochemistry of the gas-phase reactions between CHF₂CF₂OCH₂CF₃ and OH radical using a new hybrid density functional M06-2X/6-31+G(d,p) and G2(MP2)//M06-2X/6-31+G(d,p) methods. The most stable conformer of CHF₂CF₂OCH₂CF₃ is considered in our study and the possible H-abstraction reaction channels are identified. Each reaction channel shows an indirect H-abstraction reaction mechanism via the formation of pre-reactive complex. The rate coefficients are determined for the first time over a wide range of temperature 250–1000 K. At 298 K, the calculated total rate coefficient of k_OH = 1.01×10^?14 cm³ molecule^?1 s^?1 is in good agreement with the experimental results. The heats of formation for CHF₂CF₂OCH₂CF₃ and CF₂CF₂OCH₂CF₃ and CHF₂CF₂OCHCF₃ radicals are estimated to be -1739.25, -1512.93 and -1523.94 kJ mol^?1, respectively. The bond dissociation energies of the two C-H bonds are C(-H)F₂CF₂OCH₂CF₃: 423.34 kJ mol^?1 and CHF₂CF₂OC(-H)HCF₃: 411.87 kJ mol^?1. The atmospheric lifetime of CHF₂CF₂OCH₂CF₃ is estimated to be around 4.5 years and the 100-year time horizon global warming potentials of CHF₂CF₂OCH₂CF₃ relative to CO₂ is estimated to be 601.     

One‐Dimensional Magnetic Composite of Polypyrrole‐Containing Carbon Nanotubes/Ni0.75Zn0.25Fe2O4

A novel one‐dimensional electromagnetic nanocomposite of polypyrrole (PPY) containing carbon nanotubes (CNTs)/Ni_0.75Zn_0.25Fe₂O₄ was synthesized by an in‐situ polymerization method. The composite was characterized by x‐ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared. The XRD results confirmed that PPY, CNTs, and Ni_0.75Zn_0.25Fe₂O₄ coexisted in the composite. The TEM and HRTEM results indicated that PPY coated the surface of the CNTs/Ni_0.75Zn_0.25Fe₂O₄ with a thickness of 15–30 nm. The lattice spacings, according to the first main peak of the CNTs, Ni_0.75Zn_0.25Fe₂O₄, and PPY, was about 0.34 nm, 0.25 nm, and 0.42 nm, respectively. The FTIR result also indicated that the PPY formed in the composite. A test of magnetic properties indicated that the composite was ferromagnetic with the saturated magnetization of 12.86 electromagnetic units (emu)/g, and the coercive of 127.18 Oersted (Oe).     

Ab initio study of the linear and nonlinear optical responses in BiAlO3

The linear and non-linear optical properties of BiAlO₃ are studied by employing the density functional perturbation theory within the local density and generalized gradient approximations. The computations are based on the electronic structure obtained within density functional theory. The optical properties such as the dielectric function, refractive index, spectral reflectivity, absorption coefficient and electron energy-loss spectrum are obtained in the energy region of up to 30 eV. The calculated value of the birefringence for BiAlO₃ shows that it is a uniaxial negative crystal and has a large birefringence. We also report our studies on the second harmonic generation response coefficient over a large frequency range for BiAlO₃ crystal. The predicted second-order optical spectra indicate pronounced structures related to of 1ω and 2ω frequency resonances. Furthermore, the non-linear optic and linear electro-optic coefficients are computed by employing 2n + 1 theorem applied to an electric-field dependent energy functional. The results are compared with the available calculations.     

SEM and TEM analysis of composite of ZrO2-Ti system

3Y-ZrO₂-Ti composites obtained by slip casting method were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, the Vickers hardness was measured. The experiments show the complex microstructure of composites. The tetragonal zirconium dioxide (t-ZrO₂) and monoclinic zirconium dioxide (m-ZrO₂) as a composite matrix were detected at XRD analysis. SEM observations revealed that Ti -rich phase are uniform distributed in composites. Moreover, the large and very fine precipitations were found. The very fine Ti rich precipitations were located at ZrO₂ grain boundaries as well as in the triple-points. TEM experiments confirmed that in the sintered composites 3Y-ZrO₂ – 10%Ti the uniaxial ZrO₂ grains (100–600 nm), fine monoclinic martensitic plates and fine round monoclinic particles (20–40 nm) of ZrTiO₂ phase were exist. The complex microstructures of 3Y-ZrO₂-Ti composites have a high hardness as a result of existing fine ZrTiO₂ and other Ti oxides precipitations.     

X-ray study on the phase transitions in triammonium hydrogen disulfate crystals and deuterated crystals

The structural phase transitions in triammonium hydrogen disulfate crystals and deuterated crystals below room temperature have been studied by X-ray diffraction. Three phases are observed in the temperature range from 25°C down to — 160°C. The space groups in three different phases are identified as C2/c, P2/n (or Pn), and C2 for (NH₄)₃H(SO₄)₂ and (ND₄)₃D(SO₄)₂ crystals. No isotope effect on the structural phase transitions in these crystals could be detected by these studies. The occurrence of structural phase transitions caused by the reorientation of SO₄ groups and/or the shift of oxygen atoms from the sulfate atom in the SO₄ group are suggested from the diffraction photographs.     

Microwave-assisted synthesis and magnetic property of magnetite and hematite nanoparticles

Nanoparticles of magnetite (Fe₃O₄) and hematite (α-Fe₂O₃) have been prepared by a simple microwave heating method using FeCl₃, polyethylene glycol and N₂H₄·H₂O. The amount of N₂H₄·H₂O has an effect on the final phase of Fe₃O₄. The morphology of α-Fe₂O₃ was affected by the heating method. Crystalline α-Fe₂O₃ agglomerates were formed immediately at room temperature and most of these nanoparticles within agglomerates show the same orientation along [110] direction. After microwave heating, ellipsoidal α-Fe₂O₃ nanoparticles were formed following an oriented attachment mechanism. Both Fe₃O₄ and α-Fe₂O₃ nanoparticles exhibit a small hysteresis loop at room temperature.     

Sequence and Hot Transitions in the Co2 Molecule; Interference of Adjacent Lines Belonging to Different Transitions as a Function of Temperature

Carbon-dioxide spectra of some higher transitions in the 9-11μm region were studied. Spectra of the sequence ([10°1,02°1]_I,II - 00°2) and hot (01¹1 - 11¹0) bands were calculated as a function of temperature. the positions of the ro-vibrational transitions and their intensities were determined as a function of temperature. for lines in hot and sequence transitions whose positions are close to some of the regular lines ([l0⁰0,02⁰0]_I,II - 00°1)¹ absorption coefficients of adjacent lines were calculated as functions of line center distances and temperature. the resulting values of the absorption coefficient for conditions of constant pressure or constant volume were determined.     

Nanocomposites of Poly(vinyl alcohol) Reinforced with Chemically Modified AL2O3: Synthesis and Characterization

The surface of α-alumina (Al₂O₃) nanoparticles was first modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a series of poly(vinyl alcohol)/ surface modified Al₂O₃ nanocomposite suspensions were prepared in ethanol by a simple ultrasonic irradiation process. Composite films with 5, 10, and 15 wt % of inorganic Al₂O₃ nanoparticles were achieved after solvent evaporation. The formation of the composite materials were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and optical transparencies. The FE-SEM and TEM results showed a homogenous dispersion of nanoscale inorganic particles in the poly(vinyl alcohol) matrix. TGA thermographs showed that the thermal stability of the prepared Al₂O₃-reinforced nanocomposites was improved, increasing with increasing content of the nanoparticles. According to the optical transparencies, the optical clarity of poly(vinyl alcohol)/Al₂O₃ nanocomposite films was only slightly affected by the presence of the Al₂O₃ content.