Langmuir-Blodgett films containing carotenoid dye. II. Structure and conducting characteristics of ethyl β-apo-8-carotenoate/cadmium stearate LB films

The structure, doping, and electrical conductivity characteristics of ethyl β-apo-8-carotenoate dye (EA8C)/cadmium stearate Langmuir-Blodgett (LB) films were investigated. The EA8C/cadmium stearate mixed multilayer thin films, with the molar ratio of 1 : 4, prepared at subphase pH 6, exhibited well-defined layered structures as determined by X-ray diffraction (XRD) spectra. The mixed LB films went ready doping upon exposure to iodine vapor or dipping in sulfuric acid solution. The UV/VIS and XRD data showed that the incorporated EA8C was thermally stable up to 80°C. The best conductivity characteristics were obtained with the iodine vapor. Thus, the mixed LB films exposed to iodine vapor showed in-plane and transverse conductivities of 10^-6 and 10^-7–10^-8 S/cm, respectively. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 619–624, 1997     

Electrochemical characteristics of lithium metal anodes with diamond like carbon film coating layer

To overcome the poor electrochemical characteristics of lithium metal anodes due to the dendrite formations, diamond like carbon (DLC) films were deposited onto the surface of lithium metal by radio frequency-plasma enhanced chemical vapor deposition (CVD) technique using acetylene gas as carbon precursor. The substrate temperature was selected as the main experimental parameter to control the bonding characteristic (sp²/sp³ ratio) of the films. The presence of diamond like structures was confirmed by Raman and Fourier transform infra red spectroscopy. The DLC coated lithium metal was then characterized as an anode material for lithium secondary batteries. The results showed that the DLC coated lithium metal anodes exhibited better electrochemical characteristics in terms of higher specific capacity and smaller interfacial impedance. These improved characteristics were attributed to the presence of DLC film coating which might suppress the dendrite's formation by protecting the lithium metal surface from the direct contact with the electrolyte.     

Electrical characterization of p-type cubic boron nitride/n-type silicon heterojunction diodes

Nanocrystalline p-type cubic boron nitride/n-type silicon diodes with three different interfaces were fabricated by plasma chemical vapor deposition and ultrahigh-vacuum bias sputter deposition. When the interface contained a t-BN layer of 25 nm thickness or less, rectification ratios as high as 4×10⁴ at room temperature and 10 at 570 K were observed. Even when the interface contained a 1–2-nm-thick insulating layer, diode characteristics were also observed but with a lower rectification ratio of 5×10². The carrier conduction at the interface was characterized primarily by thermal excitation, where barrier height altered with bias voltage similar to the case of an ideal n-Si/p-c-BN heterojunction in the temperature range of 300–570 K.     

Determination of the Vapor Density of Triacetone Triperoxide (TATP) Using a Gas Chromatography Headspace Technique

Using a GC headspace measurement technique, the vapor pressure of TATP was determined over the temperature range 12 to 60 °C. As a check on the experimental method, TNT vapor pressure was likewise computed. Values for TNT are in excellent agreement with previous published ones. For TATP the vapor pressure was found to be ~ 7 Pa at ambient conditions. This value translates to a factor of 10⁴ more molecules of TATP in air than TNT at room temperature. The dependence of TATP vapor pressure on temperature can be described by the equation log₁₀P(Pa)=19.791−5708/T(K). Its heat of sublimation has been calculated as 109 kJ/mol.     

Sorption and permeation properties of water and ethanol vapors in poly[bis(trifluoroethoxy)phosphazene] (PTFEP) membranes

The permeability and solubility for water and ethanol in PTFEP membranes were determined experimentally, and the data were analyzed by the solution-diffusion model. The permeability for water and ethanol ranged from several hundreds to several thousands Barrers, and they increased exponentially with the vapor activity and increased with temperature. At the same temperature and vapor activity, the permeability ratio between water and ethanol ranged from 5.7 to 2.3, and it decreased as the vapor activity increased. The sorption isotherms for water and ethanol were fitted by the Henry’s law relationship. The solubility decreased as the temperature increased so that the heat of sorption for both water and ethanol was negative. The solubility for water was more than twice the solubility for ethanol. The solubility seems to be inversely proportional to the molecular size of the penetrants in such a system. The solubility ratio between water and ethanol is smaller than their molecular volume ratio possibly due to the slightly stronger nonpolar interaction and the higher degree of plasticization in the ethanol-polymer system. The diffusivity for water and ethanol ranged from 10⁻⁸ to 10⁻⁷ cm²/s, and the values for water were larger than those for ethanol at the same temperature and vapor activity. The diffusivity for water and ethanol also increased exponentially with the vapor activity. The diffusivities for water and ethanol increased with temperature and their activation energies of diffusion were very similar possibly due to the same energy characteristic of polymer main chain movement.     

Characterization of some trimethyl(organylamino)silanes—precursors for preparation of silicon carbonitride films

A series of aminosilanes has been synthesized by the reaction of carboxylic acid di(organyl)amides with trimethyliodsilane. A purification method providing an increase in the yield of end products to 82% has been developed. The identity of the products has been confirmed using an elemental analysis and IR, UV, and ¹H NMR spectroscopy. The spectral characteristics of the synthesized aminosilanes have been determined. The temperature dependences of the saturated vapor pressure have been established, and the thermodynamic characteristics of the vaporization processes have been calculated. It has been demonstrated that the aminosilanes Me₃SiNEt₂, Me₃SiNHAll, and Me₃SiNHPh are heat resistant in the temperature range 296–452 K and have a vapor pressure sufficient for their use in the processes of chemical vapor deposition of a substance, so that they can be recommended as precursors for synthesis of silicon carbonitride films.     

The Deposition of Unattached Radon Progeny in a Tracheobronchial Cast as Measured with Iodine Vapor

ABSTRACT

The deposition of the unattached radon progeny in hollow cast models of the human tracheobronchial region was studied using iodine vapor. The experiments were conducted in a replicate cast whose inner surface was coated with NaOH impregnated charcoal powder. This coating can trap iodine molecules by converting iodine into iodide and iodate, so that the iodine gas molecules behave like particles and stick to the surface upon contact. The iodine vapor is selected as a surrogate of radon progeny because the effective diffusion coefficient of iodine vapor, 0.08 cm² s^?1, is close to the diffusivities of unattached radon progeny (0.03–0.07 cm² s^?1). Deposition experiments have been conducted under constant and cyclic inspiratory flow between 5 and 30 LPM. It was found that the deposition of iodine vapor under constant flow can be described by diffusion in laminar flow. The cyclic inspiratory flow pattern does not significantly change the total deposition in the tracheobronchial cast. This observation, combined with the enhanced particle deposition due to charge (Cohen et al., 1996) suggest that particle charge plays an important role in the deposition of submicron particles in human airways.     

High-density plasma chemical vapor deposition of amorphous carbon films

This work investigated the influence of the plasma parameters pressure and RF power on the characteristics of amorphous carbon films deposited by high-density plasma chemical vapor deposition, using inductively coupled methane plasmas. These films show several good electrical characteristics: high resistivity, low dielectric constant and high breakdown field. After deposition, the films were characterized as follows: the thickness was measured with a step height meter and an ellipsometer; Fourier transform infrared spectroscopy was used to identify the sp² and sp³ hybridization of C and CH bonds and other possible bonds that can appear because of the hydrogen presence; atomic force microscopy was used to measure the film roughness and I–V and C–V measurements to determine the dielectric constant, the electric resistivity and the breakdown electric field. The films deposited with high-density plasmas showed good characteristics for several applications, when compared to deposition with conventional RF plasmas. These films show a better structural quality with a high sp³ to sp² ratio. Even with this high sp³ to sp² ratio, the RMS surface roughness of an approximately 300 nm thick film was only 0.24 nm. For microelectronic applications, a very low dielectric constant of only 1.68 and a high resistivity of 1.5×10¹⁴ Ω cm were obtained.     

<Emphasis Type="Italic">N</Emphasis>-bromohexamethyldisilazane: Investigation of properties and thermodynamic simulation of precipitation of thin-layer structures from the vapor phase

N-Bromohexamethyldisilazane has been characterized using an elemental analysis and IR, UV, ¹H NMR, ¹³C NMR, and ²⁹Si NMR spectroscopy. The spectral characteristics of the compound have been determined and the saturated vapor pressure has been measured. The thermodynamic simulation of the chemical vapor deposition (CVD) of silicon carbonitride films in the Si-C-N-Br-H system has been performed at low pressures (13.30 and 1.33 Pa) over a wide temperature range (from 400 to 1200 K) with the use of initial gas mixtures of N-bromohexamethyldisilazane with hydrogen and ammonia. The possibility of preparing films of different compositions has been demonstrated and the optimum conditions for deposition of silicon carbonitride coatings of the general composition SiC _x N _y have been established.     

Correlation of water vapor adsorption behavior of wood with surface thermodynamic properties

To improve the overall performance of wood–plastic composites, appropriate technologies are needed to control moisture sorption and to improve the interaction of wood fiber with selected hydrophobic matrices. The objective of this study was to determine the surface thermodynamic characteristics of a wood fiber and to correlate those characteristics with the fiber's water vapor adsorption behavior. The surface thermodynamic properties, determined by inverse gas chromatography at infinite dilution or near zero surface coverage, were the dispersive component of the surface energy, surface acid‐base free energy and enthalpy of desorption of acid‐base probes, and surface acid‐base acceptor and donor parameters (K_A and K_D). Water vapor adsorption was expressed in terms of the percentage of weight gain (ΔW%) resulting from water vapor adsorption on the wood particles, calculated relative to their initial weight after preconditioning in a vacuum dessicator at room temperature. The results showed a strong correlation between ΔW% and K_A, and between ΔW% and surface acid‐base free energy of water desorption (ΔH^AB_water), calculated from experimental K_A and K_D and values in the literature for acceptor and donor values of water. These results suggest that for substrates such as wood, whose surface Lewis acid‐base properties are characterized by a relatively stronger tendency to accept electrons, the key to controlling water vapor adsorption is to manipulate the magnitude of ΔH^AB_water, primarily via K_A, and to a lesser extent via K_D. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 399–407, 1999     

螺旋板换热器轴向错流通道湿法捕尘拟均相模型

提出了螺旋板换热器轴向错流通道冷却冷凝湿法除尘的方法,指出了PM_2.5在尾气对流传热传质边界层内热泳和伴随水蒸气冷凝的扩散泳运动特征和冷凝液膜吸收除尘机理并建立了拟均相模型,获得了PM_2.5浓度衰减函数和以冷凝通量n_w为参数的捕尘效率模型。通过“三传”类比获得了从尾气流速求取模型参数的方法,并通过恒壁温条件下冷却冷凝实验数据验证了模型参数计算方法的正确性,结果表明水蒸气组分扩散体积通量即PM_2.5扩散泳速度V_w是控制性参数,其值在20～40 mm·s^-1范围。     

Vapor pressure and heat of solution of sulfur dioxide in 1-methyl-2-pyrrolidone and its aqueous solution

A new method was developed to measure the vapor pressure of sulfur dioxide above various liquid absorbents. It was applied to pure 1-methyl-2-pyrrolidone and its aqueous solution at 50°C to 91°C for SO₂ loadings of 3.73 × 10 ⁴ kg/kg to 2.16 × 10 ⁻² kg/kg. A chemical model was developed. The heat of solution was calculated from the dependence of the vapor pressure on temperature and was 3.98 × 10⁷ J/kmol (exothermic) for pure 1-methyl-2-pyrrolidone. The vapor pressures disagreed with the only previously published set of results but were confirmed by independent measurements with a gas chromatograph.     

Composites of carbon black functionalized with polymers as candidates for the detection of methanol vapor

Homo- and copolymers of styrene and 4-vinylpyridine prepared by a nitroxide-mediated “living” free-radical method were grafted onto carbon black (CB) by trapping of radicals formed by the dissociation of the radical-capped polymers. The structural characteristics of the polymers and the composites were investigated by using Fourier transformed infrared spectra, nuclear magnetic resonance spectra, thermal gravimetric analysis, scanning electron microscopy and gel permeation chromotography. The composites were dip-coated on interdigitated electrodes to prepare thin film gas sensors, and their electrical responses towards methanol vapor were investigated at room temperature. It was found that the composites exhibited linear and reversible electrical responses towards methanol vapor in the range of 1000–20,000 ppm (R² = 0.999), and the sensitivities are highly dependent on the structure of the polymers, the content of CB and the dispersion of CB in the composites.     

Determining the Vapor Pressures of Diacetone Diperoxide (DADP) and Hexamethylene Triperoxide Diamine (HMTD)

The vapor signature of diacetone diperoxide (DADP) and hexamethylene triperoxide diamine (HMTD) were examined by a gas chromatography (GC) headspace technique over the range of 15 to 55 °C. Parallel experiments were conducted to redetermine the vapor pressures of 2,4,6‐trinitrotoluene (TNT) and triacetone triperoxide (TATP). The TNT and TATP vapor pressures were in agreement with the previously reported results. Vapor pressure of DADP was determined to be 17.7 Pa at 25 °C, which is approximately 2.6 times higher than TATP at the same temperature. The Clapeyron equation, relating vapor pressure and temperature, was LnP (Pa)=35.9−9845.1/T (K) for DADP. Heat of sublimation, calculated from the slope of the line for the Clapeyron equation, was 81.9 kJ mole⁻¹. HMTD vapor pressure was not determined due to reduced thermal stability resulting in vapor phase decomposition products.     

The chemical vapor infiltration of exfoliated graphite to produce carbon/carbon composites

Chemical vapor infiltration was used for the production of carbon/carbon composites based on exfoliated graphite and pyrolytic carbon. Two different exfoliated graphites compacted to densities of 0.05–0.4 g/cm³ were used as a preform. The influence of the synthesis conditions (temperature, pressure, time etc.) on the degree of infiltration, the pyrolytic carbon morphology and the C/C composite characteristics was examined using Raman spectroscopy, scanning electron microscopy and low-temperature nitrogen adsorption.     

Novel gas sensor from polymer‐grafted carbon black: Vapor response of electric resistance of conducting composites prepared from poly(ethylene‐block‐ethylene oxide)‐grafted carbon black

A crystalline block copolymer of poly(ethylene‐block‐ethylene oxide) (PE‐b‐PEO) was successfully grafted onto a carbon black surface by direct condensation of its terminal hydroxyl groups with carboxyl groups on the surface using N,N′‐dicyclohexylcarbodiimide as a condensing agent. The electric resistance of the composite from PE‐b‐PEO (PEO content is above 50 wt %)‐grafted carbon black drastically increased to 10⁴–10⁶ times of the initial resistance in a vapor of dichloromethane, chloroform, tetrahydrofuran, and carbon tetrachloride, which are good solvents for PE‐b‐PEO, and returned immediately to the initial resistance when the composite was transferred in dry air. However, the change of the electric resistance of these composites was less than one‐tenth in a poor solvent vapor at the same condition. The response of the electric resistance was reproducible and stable even after exposure to a good solvent vapor and dry air with 30 cycles or exposure to the vapor over 24 h. The effect of PEO content on the vapor response was also investigated. The composite from PE‐b‐PEO‐grafted carbon black responded to the low vapor concentration with a linear relationship between the electric resistance and the concentration of the vapor in dry air. This indicates that the composite can be applied as a novel gas sensor. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2437–2447, 2000     

Vapor specific extents of uptake by nanometer scale charged particles

The uptake of vapor molecules by nanometer scale aerosol particles (clusters) is of fundamental importance in aerosol science; uptake is the first step of condensational growth in both the ambient as well as in condensation based particle detectors. However, uptake is not well understood at the nanometer scale. We examined the uptake of organic vapor molecules by nanometer scale sodium chloride cluster ions ((NaCl)_x(Na⁺)_z and (NaCl)_x(Cl^?)_z) using a differential mobility analyzer coupled with a time-of-flight mass spectrometer. Through monitoring cluster ion inverse mobilities as functions of solvent vapor pressure in the mobility analyzer, the extent of uptake was monitored for 1-butanol, ethanol, methyl ethyl ketone (MEK), and toluene. With butanol vapor pressures in the <300 Pa range, shifts in inverse mobility in excess of a factor of 2 were observed for nearly all examined clusters. Ethanol and MEK uptake led to shifts for positively charged cluster ions upwards of a factor of 1.5. Ethanol exposure led to similar sized shifts for negatively charged clusters ions, while MEK exposure led to negative ion inverse mobility shifts less than a factor of 1.3. Toluene was sorbed much less efficiently than the other solvents; toluene exposure led to shifts in inverse mobility below a factor of 1.2. In total, relative inverse mobility shifts, which are direct functions of the extent of vapor uptake, were found to be only weakly dependent on cluster ion size when compared to the influence of vapor molecular structure and cluster ion charge polarity. Classical (Kelvin-based) models are found inadequate to explain the observed mobility shifts, and we instead used a site-specific, Langmuir type model to describe the vapor uptake behavior by the cluster ions.

© 2017 American Association for Aerosol Research     

Vapor Permeation and Pervaporation of Aqueous 2‐Propanol Solutions through the Torlon® Poly(amide imide) Membrane

Abstract

In the present study, vapor permeation and pervaporation of aqueous 2‐propanol mixtures were investigated using Torlon^® poly(amide imide) as a membrane material. Torlon membranes preferentially permeated H₂O from aqueous 2‐PrOH mixtures both by vapor permeation and pervaporation. Diffusion experiments led to the conclusion that both solubility selectivity and diffusivity selectivity showed a preference for H₂O. Solubility selectivity is by far the dominant factor governing permselectivity, and as a result, Torlon membranes showed permselectivity toward water in vapor permeation and pervaporation. The present study showed that Torlon^® poly(amide imide) is a membrane material potentially applicable to the dehydration of water miscible organics.     

Kinetics of the catalytic destruction of cyanogen chloride

The catalytic destruction of cyanogen chloride (CNCI) in air has been investigated in a fixed-bed microreactor using a 2.15% Pt/α-alumina catalyst. If the feed stream contains water vapor, CNCl conversion as high as 98% can be achieved at 375°C and 170 000 cm³ h⁻¹ g⁻¹ space velocity. In contrast, the CNCl conversion in a dry inlet gas stream is 20% at 440°C and 46 000 cm³ h⁻¹ g⁻¹ space velocity. Water vapor in the feed stream significantly enhances the conversion of CNCl by providing an alternate hydrolysis pathway for destruction. It also promotes the complete conversion of CNCl to CO₂ and HCl with negligible selectivity to CO and Cl₂. The CNCl conversion decreases with increasing concentration in the feed stream. A kinetic model of the form r = kC_a/1(1 + K_pC_p) adequately represents the data in the presence of water vapor.     

Tribological study of boron nitride films

Boron nitride (BN) films with different cubic and hexagonal phase compositions were deposited on silicon substrates via diamond interlayers by magnetron sputtering and electron cyclotron resonance microwave plasma chemical vapor deposition. The tribological behaviors of the BN films were investigated systematically using a ball-on-disc tribometer with silicon nitride as the counterpart. Comparison studies were also performed on sintered cubic and hexagonal BN compacts. The influence of phase compositions and surface roughness of BN coatings on their tribological characteristics was studied. The cubic BN (cBN) films showed excellent wear resistance against silicon nitride. The wear rate of the cBN films was estimated to be about 1.0 × 10^?7 mm³/N m by measuring the cross-sectional area of the wear track after the sliding test over a distance of 12 km.