Hydrogen Chloride Vapor Research Articles

Silver nanowire-based transparent, flexible, and conductive thin film

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles.

ENVIRONMENTAL BIOLOGY AND PATHOPHYSIOLOGY OF CADMIUM

Cadmium (Cd) is a soft, silver-white metal being together with zinc and mercury in group II b in the periodic table. It's melting and boiling point are 320.9 0 C and 765 0 C, respectively. Cd is rapidly oxidized into cadmium oxide in the air. When reactive gases such as carbon dioxide, sulphur dioxide, sulphur trioxide and hydrogen chloride or water vapour are present in the air, cadmium vapour reacts to produce cadmium carbonate, cadmium sulphite, cadmium sulphate, cadmium chloride or cadmium hydroxide. These compounds may be formed in chimneys and emitted into the environment. It is indicated that zinc-bearing coals of the central United States and carboniferous age coals of other countries contain large sub economic resources of cadmium. Although some cadmium compounds such as acetate, chloride and sulphate are soluble in water; cadmium oxide, carbonate and sulphide are insoluble.

Nanostructured Aggregates of meso-Tetramesitylporphyrin on Solid Substrate

We report aggregated nanostructure formation of water insoluble meso-tetramesitylporphyrin (MTMP) induced by hydrogen chloride (HCl) vapor on a glass plate. The formation of aggregated nanostructures of MTMP was confirmed by UV-vis, time-resolved emission spectral techniques, atomic force microscopy (AFM), and high resolution transmission electron microscopy (HR-TEM). Exposure of HCl vapor to a thin film of MTMP coated on a glass plate resulted in a 35 nm red shift of the Soret band in contrast to the case of MTMP thin film. AFM images showed the formation of MTMP aggregates induced by HCl vapor with the size of 50-170 nm in height and an average width of 120 nm. Protonation of MTMP coated on the glass plate by HCl molecules triggered the formation of aggregated nanostructures on the glass plate. Interestingly, it was found that the aggregates were not reverted back to the original morphology of MTMP thin film when it was deprotonated by exposure to ammonia vapor. The fluorescent lifetime of the MTMP thin film was decreased from 11.48 to 0.78 ns when it was exposed to HCl vapor, indicating the formation of MTMP aggregates on the glass surface.

Optochemical sensing of hydrogen chloride gas using meso-tetramesitylporphyrin deposited glass plate

Meso-tetramesitylporphyrin (MTMP) deposited glass plate (solid state sensor) was used to sense hydrogen chloride (HCl) gas based on optochemical method. Exposure of the solid state sensor to HCl vapor results in the formation of protonated meso-tetramesitylporphyrin (PMTMP). UV–vis and fluorescence spectral techniques were used to study the protonation of MTMP in dichloromethane–methanol mixture. The optical spectra of MTMP show an intense Soret band at 418 nm with a 14 nm red shift upon protonation by HCl. Ab-initio calculations were carried out to visualize the effect of protonation on planarity and stability of the porphyrin ring. The solid state sensor was characterized by UV–vis spectral technique. The sensor exhibits characteristic Soret and Q bands for the deposited MTMP with slight red shift when compared to MTMP in dichloromethane. The concentration of gaseous HCl was monitored from the changes in the absorbance of Soret band of PMTMP at 452 nm. The detection limit of the solid state sensor towards gaseous HCl was found to be 0.03 ppm. The present solid state sensor was highly stable for several months.

Multi-hydrogenated compounds monitoring in optical fibre manufacturing process by photoacoustic spectroscopy

Sub-ppm hydrogen chloride (HCl) and water vapour (H2O) monitoring using photoacoustic spectroscopy in optical fibre manufacturing is reported. The development and performance of a sensor based on an acoustic resonant configuration is described, and on-site measurements are presented. Two DFB lasers emitting in the 1370 nm and 1740 nm range were used for the detection of H2O and HCl, respectively. A detection limit (defined for a SNR=3) of 60 ppb for HCl and 40 ppb for H2O was achieved. Contamination sources of the carrier gas used for the fibre preform manufacturing are identified and discussed.

UV-Cross-Linked Poly(vinylpyridine) Thin Films as Reversibly Responsive Surfaces

We report that UV-cross-linked poly(4-vinylpyridine) (P4VP) films acted as reversibly responsive coatings that controlled surface wettability and swelling toward external stimuli: solvent and pH. The polymer films were prepared simply by spin-coating a solution of P4VP followed by UV irradiation. These cross-linked films, when treated with chloroform, showed ∼31% increase in film thickness whereas films extracted with methylene chloride or n-butanol exhibited a slight decrease. The increase in film thickness was due to the protonation of pyridyl groups by hydrogen chloride resulting from the photodegeneration of chloroform. The film expanded to minimize repulsion around the charged centers. This hypothesis was further confirmed by exposing the cross-linked film to hydrogen chloride vapor. The film expanded ∼37% whereas no thickness increase was observed for films exposed to ammonia or methanol vapors. The extent of swelling was monitored in situ using a quartz crystal microbalance sensor. Large oscillation frequency shifts were detected when the UV-cross-linked P4VP film was exposed to acidic buffer solutions. The changes were rapid, and the effect was reversible.

Growth and characterization of thick GaN layers with high Fe doping

Thick Fe-doped GaN layers were grown by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). FeCl2 formed by the reaction between ferrocene (Cp2Fe) and HCl was introduced during GaN growth. Resistivity of the GaN layer increased with increasing Cp2Fe input partial pressure. A semi-insulating (SI)-GaN layer exhibiting room-temperature resistivity of 3.0 × 109 Ω cm was successfully prepared by compensating for the residual donors. The crystalline quality of the GaN layer was found to deteriorate with excess Fe doping. These results indicate that control of background donor impurities is critically important to grow high-quality SI-GaN layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Improvements in crystalline quality of thick GaN layers on GaAs (111)A by periodic insertion of low‐temperature GaN buffer layers

Thick and high quality GaN layer growth using periodic insertion of low-temperature (LT)-grown GaN buffer layers was investigated by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). Both morphological and optical properties of GaN epitaxial layers were drastically improved by inserting a second LT-GaN buffer layer. Also, the thickness of the second buffer layer was found to affect the quality of subsequently grown epitaxial layers. The full-width at half maximum (FWHM) value of X-ray diffraction for () plane (φ scan) of the GaN layer with double buffer layer structure decreased to 608 arcsec whereas that with single buffer structure was 3600 arcsec. These results indicate that the free-standing GaN substrate with low dislocation density can be possible by reiterating the growth sequence of buffer layer and epitaxial layer. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A Study on Monitoring of Vinyl Chloride Gas by an Indirect Sensing Method

An indirect sensing method is described for vinyl chloride with an amperometric sensor connected to a prepyrolysis column. Significant sensing ability to the pyrolyzed gas, produced from pyrolysis of 0–30 ppm vinyl chloride gas, was obtained with a Pt/porous alumina substrate assembly. Furthermore, the sensing current was proportional to the concentration of vinyl chloride gas in the investigated concentration range. The sensitivity and sensing limit for vinyl chloride were observed as functions of pyrolysis temperature, gas flow rate, and applied potential. Preferable sensing parameters were 400°C, 150 mL min−1, and 1.2 V (vs. Ag/AgCl), in which the sensing reaction was controlled by gas diffusion. Effect of porosity of porous alumina substrate on the sensing performances was also studied. The electroactive species, which was contained in the pyrolyzed gas and electrochemical oxidized on the sensing electrode, was suggested to be hydrogen chloride vapor. © 2003 The Electrochemical Society. All rights reserved.

Influence of Temperature Ramping Rate on Thick GaN Growth on GaAs (111)A Surfaces

High temperature growth of thick GaN layers on GaAs (111)A substrates was performed using a two-step growth process by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). Temperature ramping rate of the low-temperature (LT)-grown GaN buffer layer was found to be a key factor controlling the crystalline quality of subsequently grown GaN layer at high temperature. When a 50 nm thick LT-GaN buffer layer grown at 550 °C is heated to 1000 °C, it is essential to apply a temperature ramping rate of 15 °C/min or more in order to grow a high-quality GaN layer with a specular surface on a GaAs (111)A substrate.

Influence of substrate polarity on the low-temperature GaN buffer layer growth on GaAs (1 1 1)A and (1 1 1)B surfaces

Influence of substrate polarity on the low-temperature (LT)-GaN buffer layer growth on GaAs (1 1 1)A and (1 1 1)B surfaces was investigated for the two-step growth of GaN on GaAs (1 1 1) substrates. Two growth methods were studied: metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) using gallium chloride (GaCl) as the gallium (Ga) source and conventional metalorganic vapor phase epitaxy (MOVPE) using trimethylgallium (TMG) as the Ga source. A 50-nm-thick LT-GaN buffer layer grown on a GaAs (1 1 1)A surface consisted of an amorphous-like matrix including oriented crystallites in it, whereas that grown on a GaAs (1 1 1)B surface mainly consisted of oriented crystallites. After heating process up to 1000°C in the presence of NH 3, the GaAs (1 1 1)B surface covered with the LT-GaN buffer layer seriously deteriorated due to etching of GaN during the heating process. On the contrary, the LT-GaN buffer layer on GaAs (1 1 1)A surface crystallized to highly oriented GaN grains during the heating, and no deterioration of GaAs substrate occurred. These results are attributed to the difference in etching rate of GaN related to the lattice polarity of GaN on GaAs substrate. Same results were obtained for both MOHVPE and MOVPE.

Thick and high-quality GaN growth on GaAs (1 1 1) substrates for preparation of freestanding GaN

The growth of thick, high-quality GaN layers on GaAs (1 1 1)A substrates was investigated using a two-step growth process by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). The thickness and temperature ramping rate of the low-temperature (LT)-grown GaN buffer layer as well as the growth temperature of the subsequent thick GaN layer at high temperatures were found to be the key factors controlling the crystalline quality of the GaN layer on GaAs (1 1 1)A substrate. Growth of a 50-nm-thick LT-GaN buffer layer at 550°C and subsequent heating to 1000°C at a temperature ramping rate of 16.1°C/min afforded a 100-μm-thick high-quality GaN layer with a specular surface. The results indicate that a thick GaN layer can be successfully grown on a GaAs (1 1 1)A substrate at high temperatures and represent a promising technique for the preparation of freestanding GaN substrates.

Comparison of GaN Buffer Layers Grown on GaAs (111)A and (111)B Surfaces

Comparison of low-temperature (LT-) GaN buffer layers grown on GaAs {111} surfaces has been performed. LT-GaN buffer layers of 0-160 nm thickness were grown simultaneously both on GaAs (111)A and (111)B surfaces by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) at 550 °C. On GaAs (111)A surface, the LT-GaN buffer layers showed smooth surface and covered the GaAs homogeneously. On GaAs (111)B surface, however, the LT-GaN buffer layers showed rough surface with some pits, and surface roughness increased with increasing thickness of the LT-GaN buffer layer. Due to the poor morphology of the LT-GaN buffer layers on GaAs (111)B, the GaAs was eroded during subsequent heating up to 1000°C in NH 3 ambient, whereas no deterioration was observed on GaAs (111)A surfaces covered with the LT-GaN buffer layers.

Comparison of GaN Buffer Layers Grown on GaAs (111)A and (111)B Surfaces

Comparison of low-temperature (LT-) GaN buffer layers grown on GaAs {111} surfaces has been performed. LT-GaN buffer layers of 0–160 nm thickness were grown simultaneously both on GaAs (111)A and (111)B surfaces by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) at 550 °C. On GaAs (111)A surface, the LT-GaN buffer layers showed smooth surface and covered the GaAs homogeneously. On GaAs (111)B surface, however, the LT-GaN buffer layers showed rough surface with some pits, and surface roughness increased with increasing thickness of the LT-GaN buffer layer. Due to the poor morphology of the LT-GaN buffer layers on GaAs (111)B, the GaAs was eroded during subsequent heating up to 1000 °C in NH3 ambient, whereas no deterioration was observed on GaAs (111)A surfaces covered with the LT-GaN buffer layers.

Infrared Spectrum of the H3N−HCl Complex in Solid Ne, Ne/Ar, Ar, and Kr. Matrix Effects on a Strong Hydrogen-Bonded Complex

Ammonia and hydrogen chloride vapors from thermal decomposition of NH4Cl co-deposited with excess neon at 4−5 K formed the H3N−HCl complex. Strong, broad 2084 cm-1 and strong, sharp 1060.2 cm-1 absorptions are assigned to the H−Cl stretching and symmetric NH3 bending modes and weaker 2017.4 and 708.9 cm-1 bands to the overtone of the NH3 mode and the H−Cl librational fundamental of the 1:1 complex. Complementary experiments were done with neon/argon mixtures, argon, and krypton to investigate the 1:1 complex in a range of matrix environments. Vibrational assignments are supported by 15NH4Cl, ND4Cl, and 15ND4Cl isotopic substitution. The neon matrix spectrum suggests a strong hydrogen bond, slightly stronger than in the gas-phase complex, but not as strong as found in the argon and krypton matrix hosts owing to increased solvation by the more polarizable matrix atoms.

Effects of flue gas composition on the catalytic destruction of chlorinated aromatic compounds with a V-oxide catalyst

When using catalytic flue gas cleaning, several flue gas compounds may influence oxidation reactions of hazardous volatile organic compounds, possibly leading to lower reaction rates and, thus, to an uncomplete destruction. Experimental investigations were performed with regard to the influence of selected flue gas compounds, like hydrogen chloride, sulfur dioxide, oxygen, and water vapour, on the catalytic destruction behavior of chlorobenzenes under flue gas cleaning conditions of an incineration plant. For this purpose, a metal oxide catalyst was operated at different temperatures at a space velocity of 3600 h −1 in a laboratory-scale fixed bed reactor with model flue gases, and with real flue gases generated from the TAMARA waste incineration plant. The results obtained from the studies with model flue gas were analyzed with respect to reaction kinetics. These kinetics were applied for comparison with the experimental data gained in the real flue gas.

Direct formation of solid ammonium chloride particles from HCl and NH3 vapors

The possibility of direct formation of particulate ammonium chloride (NH4Cl) from ammonia (NH3) and hydrogen chloride (HCl) gases was investigated by density functional theory and ab initio methods. Equilibrium structures were determined for the clusters constructed, respectively, from one, two, and four units of NH3–HCl in the close-packed form. While a single NH3–HCl unit is a hydrogen-bonded complex, clusters of two and four NH3–HCl units closely resemble the crystal structure of NH4Cl and contain the discrete NH4+ and Cl− ions. The ionic form results from a prompt and complete proton transfer from HCl to NH3 that takes place in the larger clusters where favorable electrostatic interactions are maximized. The implications for nucleation in the pure NH3 and HCl system are discussed.

A prognostic physico-chemical model of secondary and marine inorganic multicomponent aerosols I. Model description

In this paper, the physico-chemical basics of the sectional multicomponent aerosol model SEMA are described. SEMA includes condensation and evaporation of sulphuric acid, nitric acid, hydrogen chloride, ammonia, and water vapour. The model can be applied to predictions of the chemical composition and size distribution of aqueous tropospheric secondary and marine aerosols. In SEMA, multicomponent thermodynamics and particle-size-dependent condensation and evaporation are efficiently coupled by application of a new sectional approach.

Sorption of mercury species by activated carbons and calcium-based sorbents: effect of temperature, mercury concentration and acid gases

Bench-scale studies of mercury/sorbent reactions were con ducted to understand mechanistic limitations of field-scale attempts to reduce emissions of mercury from combustion processes. The effects of temperature (60 to 140°C), sulfur dioxide (SO2, 1000 ppm), hydrogen chloride (HCl, 50 ppm), and water vapor (5% molar) on the capture of elemental mer cury (Hg°, 8 to 40 ppb) by two thermally activated carbons, and on the capture of mercuric chloride (HgCl2, 11 to 73 ppb) by two calcium (Ca)-based sorbents were examined in a fixed-bed, bench-scale system. Capture of mercury species is affected by sorbent site activity. HgCl2 is quickly adsorbed by the alkaline sites of Ca-based sorbents; sorption in combus tors will likely be kinetically limited. Hg°, however, is more effectively removed by activated carbons; here the number of active sites appears to limit removal from flue gas. SO2 and HCl were found to either enhance or reduce sorption depend ing on the species of mercury. Enhancement or Hg° capture by activated carbon is associated with formation of active car bon-chlorine or carbon-sulfur sites while reduced capture of HgCl2 is due to loss of alkaline sites through Ca-SO2 and Ca- HCl reactions.

Stratospheric Chlorine Injection by Volcanic Eruptions: HCl Scavenging and Implications for Ozone

Because the output of volatile chlorine during a major volcanic event can greatly exceed the annual anthropogenic emissions of chlorine to the atmosphere, the fate of volcanic chlorine must be known. Although numerous observations have shown that volcanoes do not significantly contribute to the stratospheric chlorine burden, no quantitative explanation has been published. Hydrogen chloride (HCI) scavenging processes during the early phases of a volcanic eruption are discussed. A plume dynamics and thermodynamics model is used to show that HCI removal in condensed supercooled water can reduce HCI vapor concentrations by up to four orders of magnitude, preventing substantial stratospheric chlorine injection.