HCl Flow Research Articles

Characteristics of Vaporization of Coal Ash Minerals Chlorinated by Gaseous Hydrogen Chloride

When heated in contact with PVC under argon gas flow, minerals in coal ash were chlorinated by HCl evolved from pyrolyzing PVC at 550−600 K and formed chlorides were vaporized above 900 K. The volatilization characteristics were thus systematically measured by heating coal ash at a rate of 10 K/min up to 1273 K in a thermogravimetric reactor under a continuous flow of HCl. The results indicated that Fe in ash was extracted nearly completely at 1000−1273 K. Complete chlorination of Ca compounds occurred above 600 K, but vaporization of CaCl2 hardly proceeded. Vaporization of chlorides of Si, Al, and Mg was also found but was much less extensive. The volatilization characteristics were explained by considering interactions among minerals, i.e., enhanced chlorination of Fe2O3 and CaSO4 by Al2O3. Fe2O3 volatilization resulted in a similarity of the mineral composition for the residual solids derived from bituminous coal ashes.

Pattern dependence in selective epitaxial Si1−xGex growth using reduced-pressure chemical vapor deposition

Pattern dependence of the growth rate and Ge content in selective epitaxial Si1−xGex growth using reduced-pressure chemical vapor deposition has been examined for the SiH2Cl2-GeH4-H2 system. Contrary to selective epitaxial Si growth where pattern dependence diminishes at low growth temperatures, the growth rate of selectively grown Si1−xGex layers depends on the ratio of the exposed Si area to the oxide-covered area on a wafer, at temperatures as low as 600 °C. The Ge content in the layers also depends on the ratio, and the dependence is greater at higher temperatures. Adding HCl to the gas phase decreases the pattern dependence of both growth rate and Ge content. Although, in terms of the growth rate, an optimum HCl flow rate for pattern-insensitive growth exists, the Ge content in the layers is always higher for the wafer with a smaller exposed area.

Growth of semi-insulating InP: Fe in the low pressure hydride VPE system

Growth of InP:Fe has been performed in a low pressure hydride VPE system at a total pressure of 2000 Pa. As a dopant, iron chloride obtained from an elemental iron source reacting with gaseous HCl has been used. Both the source reaction and the growth have been performed in a nitrogen ambient. Fe doping levels between 10 16 and approximately 10 20 cm -3 could be adjusted by varying the HCl flow over the iron source. The growth temperature has only a slight effect on the Fe incorporation mechanism. Additionally, the Fe incorporation is found to depend on the InP growth rate. I–V measurements reveal semi-insulating behaviour for samples with iron concentrations above 10 17 cm -3, leading to specific resistivities in the 10 8 Ω cm region.

Participation of endothelium-derived nitric oxide but not prostacyclin in the gastric mucosal hyperaemia due to acid back-diffusion.

1. The possible participation of prostacyclin and nitric oxide (NO) in the gastric mucosal hyperaemic response to acid back-diffusion through a disrupted gastric mucosal barrier was examined. The experiments were carried out on anaesthetized rats in which acid back-diffusion was elicited by gastric perfusion with dilute ethanol in 0.15 M HCl and gastric mucosal blood flow (MBF) was measured by the hydrogen gas clearance technique. 2. Indomethacin (28 mumols kg-1, s.c.), an inhibitor of the formation of cyclo-oxygenase products including prostacyclin, failed to alter mean arterial blood pressure (MAP), basal MBF and the hyperaemic response to acid back-diffusion in urethane-anaesthetized rats. 3. NG-nitro-L-arginine methyl ester (L-NAME; 13 and 43 mumols kg-1, i.v.), an inhibitor of endothelium-derived NO formation, increased MAP in a dose-dependent manner. Whilst basal MBF in urethane-anaesthetized rats was not changed, the increase in MBF caused by gastric perfusion with dilute ethanol in acid was dose-dependently depressed by L-NAME. The loss of H+ ions from the gastric lumen, an indirect measure of acid back-diffusion, was significantly enhanced by 43 mumols kg-1 L-NAME. In contrast, D-NAME (13 and 43 mumols kg-1) was without effect on MAP, basal and stimulated MBF, and acid back-diffusion. 4. Unlike in urethane-anaesthetized rats, L-NAME led to a significant reduction of basal MBF in phenobarbitone-anaesthetized rats. MAP in the phenobarbitone-anaesthetized rats was significantly higher than in urethane-anaesthetized rats, and the hypertensive effect of L-NAME under phenobarbitone anaesthesia was significantly smaller than under urethane anaesthesia.5. The rise in MBF brought about by acid back-diffusion was blocked by L-NAME administered to phenobarbitone-anaesthetized rats. Infusion of L-arginine (120 pmol kg -1 min- ', i.v.) led to a partial, but significant, reversal of the effects of L-NAME on MAP and the hyperaemia due to acid back-diffusion.6. These findings indicate that endothelium-derived NO plays an important mediator role in the gastric mucosal vasodilatation caused by back-diffusion whilst vasodilator prostanoids such as prostacyclin are not involved.

Chemical vapor deposition of ZnS : Tb electroluminescent films in a bypass-HCl flow system

Green-emitting ZnS : Tb electroluminescent films have been successfully grown by low-pressure chemical vapor deposition, in which a Tb source is transported as gaseous halide by using a HCl carrier gas. A secondary HCl flow, bypassing the source material, is additionally supplied to the growth ambience. It is shown that the ZnS : Tb film changes from the cubic structure to the hexagonal structure with increasing the bypass-HCl flow rate, whereas the Tb concentration is basically determined by the mass transfer of the Tb-halide. The film growth rate decreases significantly in the presence of the HCl flow, and simultaneously the crystal quality is much improved by the incorporation of the Tb-dopant. Such growth behaviors are explained by supposing two kinds of competetive relations; one is a surface migration process competing between ZnCl 2 and an isolated Zn atom, the other is a hexagonal nucleation process competing between TbCl 3 and ZnCl 2. The critical HCl flow rates to control the crystal structure are completely determined. The growth kinetics and the roles of Tb 3+ and Cl - ions are discussed on the basis of the competitive adsorption model.

Relationship between dislocation generation, vapour phase supersaturation and growth rate in InP layers obtained by vapour phase epitaxy

Abstract The interrelationship between growth conditions, dislocation generation mechanisms and layer growth rate has been studied in InP/InP layers prepared by hydride vapour phase epitaxy. In the present experiments, only the PH3 flow rate was varied, whereas the HCl flow rate was kept constant. Contrary to what is generally believed, even very low growth rates yield a very high dislocation density. The dislocations are generated by the condensation of point defects that are incorporated in supersaturation into the layer during the whole growth sequence. Under higher flow rate conditions, dislocation generation by glide processes seems to prevail. Layers with minimum defect density are obtained for intermediate PH3 flow rates. The influence of either the spiral growth or the two-dimensional nucleation mechanism on the macroscopic layer growth is discussed. A procedure to reduce the morphological defects, termed hillocks, is also suggested.

Selective epitaxial growth of silicon

We have studied selective epitaxial growth of silicon in the SiCl2H2/HCl/H2 system. Our results on growth rate and selectivity are reported here. We found that the growth rate and selectivity are strong functions of the partial pressures of HCl, SiCl2H2, H2, exposed Si area, and wafer position. We propose that growth and selectivity are controlled by surface reactions between SiCl2H2 and HCl and the SiO2 and Si surfaces. Higher HCl flow rates decrease the adsorption coefficients and/or incorporation rates of the reactive SiCl2H2(g) species on both SiO2 and Si. When either is zero for SiO2 and both are greater than zero on Si, selective depositions occur. Finally, we present data on the effect various SiO2 surface treatments have on the density and distribution of Si nuclei on this surface.

The Infrared Spectroscopic Determination of Moisture in HCl for the Characterization of HCl Gas Drying Resin Performance

A Fourier transform infrared spectroscopic method has been developed for the determination of trace moisture in HCl gas. Calibration of moisture was performed as a two-step process. First, an FT-IR spectrometer equipped with a 10-m-pathlength cell was placed in series with a DuPont 5700 Moisture Analzyer to yield an absorbance vs. concentration curve of H2O in N2. In the second step, the moisture analyzer was replaced with a water scrubber, and the correlation of molar absorbance values for moisture in HCl vs. moisture in N2 was obtained through dilution of a fixed-concentration moist nitrogen stream into alternate streams of dry HCl and N2 gas. The effects of hydrogen bonding with the HCl matrix on H2O absorbance bandwidth and intensity were investigated at 2 cm−1 and 0.5 cm−1 spectral resolutions for the O-H stretching absorbance region. Matrix correlation data resulted in a linear calibration of moisture in HCl gas for the 0.1–25 ppm range. The infrared methodology has been further utilized to characterize the performance of several HCl gas purifiers designed for use in semiconductor applications. The in-line configuration of this method permits direct quantitation of HCl gas dryer efficiency, capacity, and flow rate specifications. Instrumental considerations including corrosion-resistant optics, inert seals, fittings, valves, purge techniques, and calibration procedure details and results are discussed.

ChemInform Abstract: The Intermediacy of Re2(O2CCH3)2Cl4 in the Conversion of Re2(O2CCH3)4Cl2 to Re3Cl9.

AbstractThe title compound can be isolated as an intermediate on treating the heated Re2(OAc)4Cl2 with a slow flow of gaseous HCl.

Selective silicon epitaxial growth for device-isolation technology

Selective silicon epitaxial growth using the SiH 2 Cl 2/ HCl/ H 2 system under reduced pressure was accomplished in windows surrounded by a fine patterned insulator film on a silicon substrate. Selectivity, surface planarity, and facet formation were studied as a function of growth pressure, growth temperature, and HCl flow rate during selective epitaxial growth. Defects, which were mostly pairs of stacking faults, were observed along sidewalls. The defect density in the epi-layer decreased with both decreasing growth temperature and increasing HCl flow rate. Electrical properties of p-n junctions fabricated in the epi-layers were investigated. Polysilicon gate MOSFETs were successfully fabricated on the epitaxial silicon layers. It was revealed that the selective epitaxial growth isolation was effective to reduce latch-up susceptibility for CMOS circuits. It has been discovered that the selective epitaxial growth is applicable to fine and deep isolation and can realize submicron geometry isolation for VLSI.

Thermodynamic factors that influence the lattice matching of InGaAs to InP

The change in the fraction of the HCl flowing over the gallium boat necessary to maintain the lattice matched composition of InGaAs to InP under equilibrium conditions is computed for different source and deposition temperatures, HCl flow rates over the indium, amounts of unreacted HCl, and AsH 3 flow rates. These results are compared with the experimentally determined trends found in the literature. With the exception of the decreasing HCl(Ga) fraction with increasing AsH 3 flow rates, the experimental results can be explained thermodynamically when the effects of the unreacted HCl are taken into account. Increasing the amount of unreacted HCl substantially decreases the HCl(Ga) fraction necessary for lattice matching. This relatively strong effect can, in part, explain why the lattice matching HCl(Ga) fraction for different systems can be very different for seemingly similar growth conditions. The large differences in the computed values using different thermodynamic data and the effects of ignoring the HCl in equilibrium with the liquid metals, the As 2, AsH 3, InCl 2, InCl 3, and GaCl 3 species are briefly discussed.

Probes of parietal cell function

The site of acid secretion in the gastric mucosa has been inferred, but never proven. Using differential interference-contrast (Nomarski) microscopy an expansion of intracellular vacuoles was observed in the parietal cells of living rabbit gastric glands following histamine stimulation. A similar vacuolization occurring only in part of a parietal cell population could be induced by high concentrations of accumulated weak base, aminopyrine, in the absence of secretagogue. In high-K+ medium, 10(-3) M aminopyrine induced massive vacuolization in all parietal cells, consistent with the strong effect of high K+ in stimulating aminopyrine uptake by isolated glands. Electron micrographs showed that the apparent vacuoles correspond to the secretory canaliculi in various stages of swelling. Acridine orange, a fluorescent dye which is distributed across natural membranes as a function of a pH gradient and binds in a multimolecular fashion (stacking) to negative sites, was accumulated by gastric glands as a function of acid secretion. Visualization of such glands by fluorescence or a combination of Nomarski and fluorescence microscopy showed a red fluorescence in the expanding secretory canaliculi that was in sharp contrast to the green fluorescence in the rest of the cell. From these data it is concluded that the site of acid secretion is indeed the secretory canaliculus of the parietal cell. It is also possible that the formation of secretory canaliculi may be induced osmotically and that the peripheral "parietal" position and triangular shape of the parietal cell is necessary to allow expansion and oriented apical flow of HCl.

F-atom concentration measurement via HCl titration

Titration of F atoms with HCl is shown to be described principally by the reaction, F + HCl → HF + Cl. This conclusion is arrived at by observing the effect of HCl titration on the intensity of an F-atom ESR signal, the signal intensity being proportional to F-atom concentration. The intensity decreases linearly with increasing HCl flow and (1.07 ± 0.12) HCl molecules are required for removal of each F atom. Since the titration volume contains F2 as well as F, this latter result demonstrates the secondary importance of the competing reaction, Cl + F2 → ClF + F. Accordingly, F-atom concentration may be determined in the presence of F2 by addition of an excess amount of HCl, thereby converting the F present to HF, and measurement of the amount of HF present by laser optical absorption methods. This alternative (to ESR) technique is important with regard to evaluating HF/DF chemical laser systems where F and F2 are present.

Population inversion of rotational levels of diatomic molecules due to adiabatic expansion of a gas

It is shown for the first time that a population inversion of rotational levels of diatomic molecules can be obtained as a result of adiabatic expansion of a gas mixture. The inversion is a consequence of the kinetics of the rotational relaxation of molecules in a monatomic gas. The results of numerical calculations are given for different conditions of flow of HCl+He mixtures and allowance is made for one- and twoquantum collisional transitions. One-quantum radiative transitions from inverted levels j = 13?20 are found to be located in the wavelength range ?= 40?20 ?.

Influence of Gas‐Phase Stoichiometry on the Defect Morphology, Impurity Doping, and Electroluminescence Efficiency of Vapor‐Grown GaAs P‐N Junctions

The vapor‐hydride method of epitaxial growth permits separate control of the flow rates of both the and HCl reactant species. In the present work, these variables have been independently adjusted to provide gas‐phase compositions ranging from Ga‐rich to As‐rich. The surface defect morphology has been found to be a strong function of the HCl flow rate, changing from pits at low flow rates to hillocks at higher flow rates. In contrast, the flow rate for constant HCl flows principally affects the size of the defects. The growth rate increases slightly with increasing flow rate, but decreases with increasing HCl flow rate over the range normally used. The Se‐donor and Zn‐acceptor concentrations both decrease with increasing HCl flow rate, suggesting that crystal stoichiometry is not strongly influenced by the HCl flow rate.Electroluminescent diode efficiencies range between 0.1 and 0.5% at room temperature and between 1 and 2.6% at 80°K. Peak efficiency values have been attained with slightly As‐rich gas‐phase conditions.

Some Dynamic Considerations of a Multistage Mixer-Settler Extractor and Stripper

>A dynamic study of a 10-stage box-type mixer-settler extractor was made using the system 2.7 M rare earth chloride (RECl/sup 3/)-0.5 M di(2-ethylhexyl) phosphoric acid (HDEHP) -0.1 M hydrochloric acid. Once steady state was reached, intentional upsets of varying degree were made in the individual flow rates and interface positions to test their effect on the raffinate product concentration and on the operation of the mixer-settler. The RECl/sub 3/ (feed) flow rate was found the most important variable to be controlled followed in order of importance by the HCl flow rate (organic phase) and the settler interface positions. The dynamics of the stripping of HDEHP containing 1.5, 1.8, and 1.9 M rare earths with 4 M HCl showed that the pregnant HDEHP flow rate was the most important variable to be controlled in order to maintain steady state followed by the HCl flow rate and the settler interface positions. (auth)

Some observations on the dislocation etching of GaAs 1-χP χ epitaxial layers

The structure of GaAs 1-χP χ epitaxial layers containing up to 45 mol% GaP has been revealed by dislocation etching of {111} crystal planes. This technique has the important advantage of enabling the whole structure of the epitaxial layer to be examined simultaneously. The effect of varying the thickness of the compositionally graded region on the crystal perfection of the constant composition region is shown. Use of this technique has led to the finding that variations in the HCl flow (as well as the AsH 3 and PH 3 flows) cause a change in the crystal composition.