Showing papers on "Total pressure published in 1981"

Mechanisms of Plasma‐Enhanced Silicon Nitride Deposition Using SiH4 / N 2 Mixture

Abstract: The mechanism of plasma‐enhanced vapor deposition of silicon nitride is studied by varying process parameters, such as substrate temperature, rf power, reactant gas ratio, and total pressure. The film composition (Si, N, O, and H) is determined by electron microprobe and infrared analysis. From these analyses, it is established that the film composition is determined not only by the reactant gas ratio, but also by a combined function of the rf power and total pressure in terms of , with a system‐dependent factor. The dependence of film composition on can be related to the radical generation processes. The substrate temperature is found to affect the film composition as well. Greater substrate temperature produces films with less hydrogen and more nitrogen, and hence, higher density. The film dielectric property and plasma etching rate are both studied and found to be dependent on the film composition. Finally, a three‐step deposition mechanism, namely, radical generation, radical adsorption, and adatom rearrangement, is proposed to explain the reaction scheme, and an ion incorporation mechanism is proposed to explain the change of film physical properties.

Method of and apparatus for control of reactive sputtering deposition

Abstract: A method and apparatus for the control of reactive sputtering deposition of oxide-containing films, including the monitoring of and maintaining the constancy of the deposition rate and total pressure of the system by adjustment of the oxygen and argon input flow rates. Deposition rate is monitored by an activated quartz crystal, and behaves as a sensitive function of actual oxygen partial pressure. Stoichiometry, optical and electrical properties of the oxide-containing films are therefore controllable by maintaining constant oxygen partial pressure.

Measurement of vibrational populations in low‐pressure hydrogen plasma by coherent anti‐Stokes Raman scattering

Abstract: Coherent anti‐Stokes Raman scattering (CARS) has been applied to the measurement of vibrational populations in a low‐pressure H2 plasma. We describe the plasma generator and give some particulars of the optical arrangement. For an electron density of 2×1011 cm−3 and a total pressure of 0.13 mbar, the rotational temperature is found to be 475 K. The populations of vibrational states v = 0, 1, and 2 have also been measured. Their distribution is non‐Boltzmann. The influence of pressure and discharge parameters is briefly discussed. The instrument detection sensitivity for a given rovibrational state is about 1012 cm−3.

Reactive ion etching of LiNbO3

Abstract: We describe the reactive ion etching of LiNbO3 in gas mixtures containing CCl2F2, CF4, O2, and Ar The effects of gas composition and pressure, in the range 1–10‐μm total pressure are discussed Because it is possible to replicate fine features (∼2000 A) with control of etch profiles, we expect the process to be used for three‐dimensional patterning of LiNbO3 for electro‐optic and acoustic‐optic devices

Mechanism and kinetics of the homogeneous gas-phase thermal decomposition of methylgermane

Abstract: The homogeneous gas-phase decomposition of methylgermane has been investigated by the comparative rate-single-pulse shock tube technique at 3100 torr of total pressure between 1050 and 1250 K. Three primary processes occur: CH/sub 3/GeH/sub 3/ ..-->.. CH/sub 3/GeH + H/sub 2/ (1), CH/sub 3/GeH/sub 3/ ..-->.. CH/sub 4/ + GeH/sub 2/ (2), and CH/sub 3/GeD/sub 3/ ..-->.. CH/sub 2/ = GeD/sub 2/ + HD (3). The overall decomposition rate constant in its pressure falloff regime is log k/sub 0/ (s/sup -1/) = 13.34 - 50,420 + - 3700 cal/theta, comprised of about 40% of reaction 1, and 30% each of reactions 2 and 3; and the high-pressure rate constants for the primary processes, obtained by RRKM calculations, are log k/sub 1/ (s/sup -1/) = 14.6 - 50,400 cal/theta, and log k/sub 2/ (s/sup -1/) = 14.9 - 51,600 cal/theta, and log k/sub 3/ (s/sup -1/) = 14.7 - 51,600 cal/theta. The decomposition of the primary product methylgermylene (CH/sub 3/GeH) to CH/sub 3/ and GeH radicals increases with increasing temperature with an activation energy of about 53 kcal, while the decomposition of germylene (GeH/sub 2/) to Ge and H/sub 2/ is fast and complete at shock temperatures.

A drift chamber study of the reaction ArH++H2 →H+3 + Ar and related reactions

Abstract: Ion–molecule reactions in argon– hydrogen mixtures were studied as a function of total and partial pressures, using a drift chamber mass spectrometer. The rate coefficient of the title reaction was found to depend on pressure, decreasing as the total pressure is increased from a value of 3.5×10−10 at low pressure to 3.5×10−11 cm3 molecule −1 s−1 at pressures greater than 0.8 Torr. This behavior is explained by the presence of vibrationally excited ArH+ ions formed in the reaction Ar+ + H2, and their deactivation by collisions with argon atoms. The thermalized ArH+ ions react with hydrogen more slowly than the excited ArH+ ions first formed. Rate coefficients for these processes and for several other ion reactions occurring in argon–hydrogen mixtures are given.

The kinetics of combustion of petroleum coke particles at 1000 to 1800 K: The reaction order

Abstract: As part of a program on the combustion of residual materials from coal liquefaction processes, a study has been made of the combustion kinetics of sized fractions of petroleum coke particles (median sizes 85 and 88 μm). Experiments were carried out at 101.3 kPa total pressure and at oxygen partial pressures between 5.1 and 30.4 kPa. Two parameters were determined: the ratio χ which is the ratio of the actual rate of combustion to the maximum possible (i.e. mass transfer limited rate) and the rate coefficient Rc, Rc is the rate of carbon oxidation per unit external surface of the particle per (unit pressure of oxygen)n and n is the apparent order of reaction. χ was found to vary inversely with oxygen pressure, a situation that can be shown analytically to occur for fractional values of n. Rc was found, using a statistical analysis, to be least dependent on oxygen pressure for a value of n close to 0.5. The conditions of the present experiment were close to those used in an earlier study of the combustion of sized fractions of petroleum coke (median sizes 18, 67 and 77 μm), when it was shown by experiment, and by calculation, that the rate was controlled by pore diffusion as well as by chemical reaction, i.e. the reaction was occurring under Zone II conditions. In the present work, particle size and density were each found to decrease with increasing burn-off in the manner characteristic of the Zone II regime. From these considerations, on the basis of the relation between the apparent (n) and true (m) order of reaction in Zone II (n=(m+1)/2) it follows that the true order is close to zero. When the results of the present and earlier work on petroleum coke are combined, the following relation between Rc and particle temperature (Tp) for combustion under the combined rate control by pore diffusion and chemical reaction is obtained. R c = A e x p [ - E a / R ¯ T p ) ] where A = 7.0 ± 0.6 kgC / [m2s(kPa O2)0.5] and Ea = 82,400 ± J/mol.

Steady pressure-flow relationship of a model of the canine bronchial tree

Abstract: Static pressure differences (deltaP) across the entire length and portions of a latex reproduction of a canine bronchial tree were measured during steady inspiratory or expiratory flow (V). The reproduction consists of a 10-cm length of trachea through bronchi of about 2 mm in diameter. The airflow was simulated by a water flow with tracheal Renolds number (Re0) in the range from 1,500 to 10,000. Loss in total pressure (deltaPt) was computed by summing deltaPt and V were well described (r greater than 0.98) by a dimensionless Rohrer equation deltaPt/deltaPd0 = A + B Re0 applicable to gas flow, in which deltaPd0 is a Poiseuille pressure drop. For expiratory deltaPt, A was about twice that for inspiration, while the values for B were nearly equal. Differences in kinetic energy between sites of static pressure measurement are important in determining loss in total pressure. Rohrer's equation is a good approximation to the phenomenological laws of steady inspiratory and expiratory flow-pressure relations in the canine bronchial tree for the range of Reynolds number investigated.

The influence of oxygen and total pressure on the surface oxidation rate of bituminous coal

Abstract: The intrinsic reaction rates of several bituminous coals and a carbon black have been studied over a range of particle temperatures (1700–2200 K), total gas pressures (55–10 atm) and oxygen mole fractions (01–05) in a conventional shock tube The surface reaction rates (based on external surface area) of the coals were observed to vary inversely with total pressure while no such dependence was noted for the carbon black In conjunction with observations of reducing diameter burnout mode and large surface reaction rate Arrhenius activation energies, these results suggest the existence of a roughsphere kinetics regime The true reaction order with respect to oxygen partial pressure measured at constant gas temperature is observed to be nearly 1/2; however, correction for the accompanying increase in particle temperature reduces the overall order to about 1/5 The true activation energies for both coals are about 34 kcal/mole over the temperature range studied When corrected for pore penetration, the intrinsic reaction rates of the coals are observed to be greater than those measured for the carbon black and those predicted by a recent correlation in the temperature range of 1500 to 2100 K

Pressure balanced stylographic pen

Abstract: Improvements in stylographic technical writing pens, particularly through a venting channel design which provides for a pressure balancing, or equalization, between an ultimate ink reservoir pressure and the total pressure at the writing tip; as writing depletes ink within the reservoir. Particularly, a venting channel, extending from the reservoir to ambient air, has the size of its cross-sectional shape vary as a function of the distance from its communication with the reservoir, with the variation calculated to offset gravitational forces attendant to a moving ink meniscus inside the vent channel. The balancing of total pressures also provides a constant ink flow through the writing tip when writing since the total pressure at the tip is maintained constant by the vent channel configuration. The present invention is characterized by the novel approach, of beginning with the insight that a varying static pressure, from a varying level of ink to a vent channel, must exactly offset by the capillary forces at the meniscus of that ink level in the vent channel, and then creating a total vent structure that can follow that relationship.

Contribution of water vapor monomer resonances to fluctuations of refraction and absorption for submillimeter through centimeter wavelengths

Abstract: Atmospheric fluctuations in temperature, humidity, and total pressure cause fluctuations in the absorption and refraction of electromagnetic waves We consider only the absorption and refraction fluctuations caused by variations in the width and strength of water monomer resonances We differentiate the absorption coefficient and refractive index with respect to temperature, humidity, and total pressure in order to obtain the coefficients that relate the fluctuations in absorption and refraction to these atmospheric parameters The resulting coefficients as well as the absorption coefficient and the refractivity are calculated by summing over all water vapor infrared resonances and are displayed graphically In the limit of low frequencies, these calculated coefficients are in good agreement with the formula for radio wave refractive index The effects of turbulent fluctuations in total pressure are usually negligible

The kinetics and the mechanism of the thermal decomposition of bis(trifluoromethyl) trioxide. The influence of carbonmonoxide on its decomposition

Abstract: The kinetics of the thermal decomposition of CF3O3CF3 has been investigated in the pressure range of 15–599 torr at temperatures between 59.8 and 90.3°C and also in the presence of CO between 42 and 7°C. The reaction is homogeneous. In the absence of CO the only reaction products are CF3O2CF3 and O2. The rate of reaction is strictly proportional to the trioxide pressure, and is not affected by the total pressure, the presence of inert gases, and oxygen. The following mechanism explains the experimental results: In the presence of CO there appear CO2, (CF3OCO)2, and CF3O2C(O)OCF3 as products. With increasing temperature the amount of peroxicarbonate decreases, while the amounts of oxalate and CO2 increase. The rate of decomposition of the trioxide above a limiting pressure of about 10 torr CO is strictly first order and independent of CO pressure, total pressure, and the pressure of the products. The addition of larger amounts of O2 to the CO containing system chaqnges the course of the reaction.

Rate parameters for CH3+ H2→ CH4+ H in the temperature range 584–671 K

Abstract: A new method of data treatment is described which permits the measurement of the rate constant for the reaction CH3+ H2→ CH4+ H (2) without any assumption of a value for the rate constant for methyl recombination. Experiments in which azomethane was pyrolysed in a large excess of hydrogen were carried out in the ranges 584–671 K and 5–26 Torr total pressure. The results can be expressed in the form log(k2/cm3 mol–1 s–1)= 11.70 – 44 kJ mol–1/(2.3 RT).The conditions for which the theory of the method is valid are discussed.

Subsonic tests of an all-flush-pressure-orifice air data system

Abstract: The use of an all-flush-pressure-orifice array as a subsonic air data system was evaluated in flight and wind tunnel tests. Two orifice configurations were investigated. Both used orifices arranged in a cruciform pattern on the airplane nose. One configuration also used orifices on the sides of the fuselage for a source of static pressure. The all-nose-orifice configuration was similar to the shuttle entry air data system (SEADS). The flight data were obtained with a KC-135A airplane. The wind tunnel data were acquired with a 0.035-scale model of the KC-135A airplane. With proper calibration, several orifices on the vertical centerline of the vehicle's nose were found to be satisfactory for the determination of total pressure and angle of attack. Angle of sideslip could be accurately determined from pressure measurements made on the horizontal centerline of the aircraft. Orifice pairs were also found that provided pressure ratio relationships suitable for the determination of Mach number. The accuracy that can be expected for the air data determined with SEADS during subsonic orbiter flight is indicated.

Vibrational disequilibrium in low pressure clouds

Abstract: Steady state vibrational populations of SiO and CO in several dilute blackbody radiation fields have been calculated as a function of total pressure, kinetic temperature, and chemical composition of the gas. An approximate calculation for polyatomic molecules has also been carried out. Vibrational disequilibrium becomes increasingly significant as the total pressure and radiation density decrease. Many regions of postulated grain formation are found to be far out of thermal equilibrium before the onset of condensation. The use of classical nucleation theory and equilibrium thermodynamics to predict the onset of condensation and the composition of the solids or the molecular composition of the gas phase in such regions therefore is very questionable and needs to be examined for each case.

Tethered submarine pressure transfer storage facility for liquified energy gases

Abstract: An improved offshore submarine storage facility in the ocean and like water bodies for storing liquified energy gases and similar liquid materials under pressure and at cryogenic temperatures is disclosed. The facility includes a two-part insulated submarine storage tank positioned at a selected depth in the water for storing said materials, wherein the two parts thereof move in a slidably sealing engagement relative to each other to form an insulated compression storage chamber. The tank also includes ambient water pressure transfer means for transferring external ambient water pressure to the materials stored therein. Mechanical pressure transfer devices increase the pressure applied to the materials stored therein to achieve a total pressure which promotes and aids maintenance of liquid state of the stored cryogenic materials. The tank further includes an extensible, seawater impermeable membrane extending between said two parts to form an enclosed space to seal off seawater from surfaces of said parts which slide relative to each other in sealing engagement. A balancing fluid is disposed in said enclosed space at a pressure equalized with ambient seawater pressure for providing further thermal insulation and for isolating the sealing surfaces from contact by seawater throughout the range of slide movement of the two parts of the storage tank. A balancing fluid recirculation jacket surrounding the tank provides another aspect of the present invention.

Phase Relations in Crystalline Ceramic Nuclear Waste Forms: The System UO2+x-CeO2-ZrO2-ThO2 at 1200°C in Air

Abstract: Steady-state phase relations in the system UO2+x-CeOz-ZrO2-ThO2 were determined for application to phase relations in high-level crystalline ceramic nuclear waste forms. Samples were treated at 1200°C at an oxygen partial pressure of 21.3 kPa and a total pressure of 101.3 kPa. Phase assemblages were found to be comprised of cubic solid solutions of the fluorite-structure type, solid solutions based on ZrO2, and orthorhombic solid solutions based on U3O8.

Kinetics for the Reaction of Hydrogen with a Plutonium‐1 Weight Percent Gallium Alloy Powder

Abstract: Kinetics for the reaction of hydrogen with plutonium-1 w/o gallium were measured using powder prepared ''in situ.'' The rates obeyed a first-order rate law and were independent of temperature from -29/degree/ to 355/degree/C. A pressure dependence proportional to P/sup //one-half/ was observed at pressures less than 1 kPa. From 1 to 70 kPa the pressure dependence rapidly decreased. Total pressure dependence could be accurately described by a Langmuir equation. Results indicate an adsorption-controlled reaction at low pressures and a reaction-controlled process at high pressure. 19 refs.

Manufacture of laminated board

Abstract: PURPOSE:To eliminate the generation of measling phenomenon and consequently obtain a laminated board with fine surface roughness by a method wherein forming pressure is lowered to a specified pressure for the specified period of time before the end of heating and, after the end of heating, a laminated board is cooled down with a cooling press under a specified pressure. CONSTITUTION:In order to obtain a laminated board by forming under heat and pressure, for the period of time ranging from 5-20min before the end of heating, the forming pressure is lowered to 30-50% of the total pressure applied hitherto. After the end of heating, a laminated board is cooled down with a cooling press under the forming pressure, which is 70-100% of the total pressure applied hitherto for forming under heat. Thus, measling phenomenon is prevented from developing and the surface roughness of the laminated board can be made fine. If the period of time under reduced pressure before the end of heating is below 5min, measling phenomenon develops. If the period just mentioned above exceeds 20min, the reduction of pressure is performed under the state that the curing of resin is insufficient, resulting in making the surface roughness of the laminated board remarkably coarse. Further, if the forming pressure is below 30% of the total pressure, the surface roughness of the resultant laminated board becomes coarse. If the forming pressure just mentioned above exceeds 50% of the total pressure, measling phenomenon develops in the resultant laminated board. Furthermore, if the forming pressure with the cooling press during the cooling under pressure after the end of heating, which is normally 70-100% of the total pressure applied for forming under heat, is below 70% of the total pressure, the surface roughness of the resultant laminated board becomes coarse.

Reactive sputter etching of Si, SiO2, Cr, Al, and other materials with gas mixtures based on CF4 and Cl2

Abstract: All etching processes require control of the relative etch rates of the mask and substrate materials. This is especially important in vacuum‐etching processes where directional etching is often obtained at the expense of increased mask etch rate. Etch rate control requires good control of the etching parameters, and here at a constant gas flow of 2×10−2 Pa m3/s we use target voltage (peak‐to‐peak) and partial pressure of reactant species as controlled variables rather than power density and total pressure, as is common practice. SiO2 and Si etch rates in CF4 with a Si target were found to vary as P1/2V2 where V is the peak‐to‐peak target voltage (varied between 0.6 kV and 2.9 kV) and P is the reactant gas pressure varied between 0.35 Pa (2.7 μm) and 14.3 Pa (110 μm). Cr and Al rates varied as V3, but were almost independent of pressure. These differences enable accurate selection of relative etch rates and appropriate masks. For instance, SiO2/Cr etch rate ratios as high as 50:1 may be achieved for 3.7 Pa...

Thermodynamic properties of uranium dioxide

Abstract: In order to provide reliable and consistent data on the thermophysical properties of reactor materials for reactor safety studies, this revision is prepared for the thermodynamic properties of the uranium dioxide portion of the fuel property section of the report Properties for LMFBR Safety Analysis. Since the original report was issued in 1976, there has been international agreement on a vapor pressure equation for the total pressure over UO/sub 2/, new methods have been suggested for the calculation of enthalpy and heat capacity, and a phase change at 2670 K has been proposed. In this report, an electronic term is used in place of the Frenkel defect term in the enthalpy and heat capacity equation and the phase transition is accepted.

Jet noise suppression by porous plug nozzles

Abstract: Jet noise suppression data presented earlier by Maestrello for porous plug nozzles were supplemented by the testing of a family of nozzles having an equivalent throat diameter of 11.77 cm. Two circular reference nozzles and eight plug nozzles having radius ratios of either 0.53 or 0.80 were tested at total pressure ratios of 1.60 to 4.00. Data were taken both with and without a forward motion or coannular flow jet, and some tests were made with a heated jet. Jet thrust was measured. The data were analyzed to show the effects of suppressor geometry on nozzle propulsive efficiency and jet noise. Aerodynamic testing of the nozzles was carried out in order to study the physical features that lead to the noise suppression. The aerodynamic flow phenomena were examined by the use of high speed shadowgraph cinematography, still shadowgraphs, extensive static pressure probe measurements, and two component laser Doppler velocimeter studies. The different measurement techniques correlated well with each other and demonstrated that the porous plug changes the shock cell structure of a standard nozzle into a series of smaller, periodic cell structures without strong shock waves. These structures become smaller in dimension and have reduced pressure variations as either the plug diameter or the porosity is increased, changes that also reduce the jet noise and decrease thrust efficiency.

Effect of total pressure gradient on unsteady-state diffusion rates of gases in porous media

Abstract: In the unsteady-state or dynamic methods of determining transfer properties of gases in porous media, a simplified isobaric diffusion rate equation of the Fick''s type has been used even for some cases with a pulse of pure gas. By measuring the pressure response at one end of a single porous pellet accompanied by a stepwise change in gas concentration at the other end, however, it is shown that a relatively large and rapid pressure gradient appears in the porous pellet. The pressure response curves are analyzed theoretically by using non-isobaric rate equations to obtain good accord between the theoretical and observed results. The effects of the appearance of the total pressure gradient on the concentration change at the pellet end and on the diffusion rate are discussed in detail.

Pressure-flow characteristics of the roots of Zea mays

Abstract: Root pressure is generally considered to be osmotic in origin. This explanation is not held by all workers, however. An alternative view contends that while an osmotic component certainly exists, the xylem concentrations are inadequate to account for the total pressure and that therefore the remainder must result from some form of active water pumping (see for example [2,4]). In the ideal method of testing this claim one would allow the root pressure to attain its maximum value, collect a sample of the xylem sap and compare its osmotic pressure to that developed by the root. Unfortunately, this is impossible with present techniques, since to develop maximum pressures requires zero flow, in which case no sap can be collected. One can, however, reduce the flow very nearly to zero and still obtain a small sample for comparison. Such an experiment was performed by collecting 50 µl samples of exudate from each of 22 plants under 2.7 bar pressure and pooling them for analysis. Since the exudation flowrate in this case was reduced to an average of only 7% of the unimpeded rate, the results should represent a close approximation to the ideal case. The osmotic pressure of the exudate collected in this way was found to be 3.2 bar above that of the bathing solution, well in excess of the applied pressure. Thus in the present instance, there is no need to assume that root pressure is generated by any means other than osmotic.

Calculation of temperature-oxygen fugacity tables for H2-CO2 gas mixtures at one atmosphere total pressure: Summary

Abstract: The initial CO 2 volumes yielding selected oxygen fugacities at specified temperatures have been computed for H 2 -CO 2 gas mixtures at one atmosphere total pressure. The calculations are based on the thermochemical data of the JANAF Tables for the species CO 2 -H 2 -H 2 O-CO-O 2 -CH 4 and are carried out using the Newton-Raphson method of successive approximation. The new values replace older ones where the effects of CH 4 in the system were treated only in an approximate manner.

Transverse-duct insertion type pressure averaging primary

Abstract: The present invention entails a transverse type pressure averaging primary device that is designed to be mounted within a duct and designed to sense both total and static pressures of fluid flow passing within the duct. More particularly, the pressure averaging primary system of the present invention includes high and low pressure lines that extend transversely across the duct and which generally includes multiple pressure sensing points along the lines for sensing both total and static pressure. In the case of the high pressure line, the respective total pressure sensing points thereof are appropriately confined within cylindrical shrouds. Selected cylindrical shrouds include extensions that extend to and are secured to the low or static pressure line for structurally integrating and reinforcing the spans of the high and low pressure lines.

Nuclear‐pumped lasing of 3He‐Xe at 2.63 μm

Abstract: Direct nuclear pumping of a 3He‐Xe laser, lasing at 2.63 μm, has been achieved. Scaling of the laser output with xenon concentration, total pressure, and thermal neutron flux has been investigated. A peak power in excess of 200 W was obtained at a total pressure of 3 atm, a gas mixture consisting of 5 % xenon and 95% 3He, and a peak thermal flux of 6×1016 n/cm2 s.