Wave Reactor Research Articles

ChemInform Abstract: The Shock Tube as Wave Reactor for Kinetic Studies and Material Systems

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Testing and modelling of a temperature front solid–gas reactor applied to thermochemical transformer

With the objective of improving the coefficient of performance (COP) of refrigeration cycles by sorption, the multisalt cycle constitutes a possible way of development. However, the achievement of a worthwhile COP requires the designing of solid–gas reactors which enable the creation of a heat wave in the direction of the heat transfer fluid flow. A test is carried out with a heat wave reactor containing one, or two reactants of different nature. It enables the analysis of the reactor operation during different phases of the cycle. The dynamic simulation model developed is validated from the test results. Its use enables estimating the performances of the multisalt reactor and of proposing improvements for its design.

Dependence of atomic layer-deposited Al2O3 films characteristics on growth temperature and Al precursors of Al(CH3)3 and AlCl3

The materials characteristics of Al2O3 films grown on a Si (100) substrate by traveling wave reactor atomic layer deposition were investigated in the growth temperature ranging from 250 to 500 °C. The Al2O3 films grown using Al(CH3)3 trimethylaluminum (TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. Both samples grown with different precursors revealed identical chemical binding state of oxidized Al and very flat surface morphology. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately six and 10 times higher than those of the film grown using AlCl3, respectively. For the Al2O3 films grown using TMA, the results showed that the impurity contents and the growth rate of the films decreased and the refractive index increased with the growth temperature. The content of impurities could be also lowered by increasing the N2 purge time after TMA pulse. However, the effect of purge time increase on the impurity incorporation was very small compared to that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400 °C, respectively. The rough estimation of H content using refractive indices and SIMS data indicated that the H content decreased from approximately 8.5 to 3.0 at. % as the substrate temperature increased from 250 to 400 °C. The Al2O3 film grown using AlCl3 and H2O at 500 °C, which contained approximately 0.5 at. % Cl, revealed a refractive index of 1.65.

The Characterization of Al2O3 Films Grown by Atomic Layer Deposition Using Al(CH3)3 and H2O

ABSTRACTThe materials characteristics of Al2O3 films grown on Si (100) substrate by traveling wave reactor atomic layer deposition were investigated at the growth temperature ranging from 250 to 500°C. The Al2O3 films grown using Al(CH3)3(TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately 7–10 times higher than those of the film grown using AlCl3. For the Al2O3 films grown using TMA, the impurity contents and the growth rate decreased and the refractive index increased as increasing the growth temperature. The effect of purge time increase on the impurity incorporation was very small compared with that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400°C, respectively. The rough estimation using SIMS data and refractive indices indicated that the H-content decreased from 8.6 at% to 2.9 at% as increasing the substrate temperature from 250 to 400°C. The Al2O3 film grown using AlCl3 and H2O at 500°C contained approximately 0.5% Cl and revealed the refractive index of 1.65.

High-temperature kinetics of Si-containing precursors for ceramic processing

Experimental investigations of high-temperature kinetics of Si-precursor molecules relevant to CVD and ceramic processing are described. Reaction systems using SiH4, Si2H6, and SiCl4 highly diluted in argon were studied in a shock tube, a high-temperature wave reactor, by monitoring in situ the concentrations of atomic or radical reactants Si, H, Cl, SiH, and SiH2. Because of the very high dilution, the measured properties are sensitive to a limited number of elementary reactions, allowing a relatively direct determination of the respective rate coefficients. Both thermal pyrolysis and laser flash photolysis methods were used to expand the investigated temperature range. An overview of the bimolecular Si-atom reactions is given.

Shock tube kinetics in homogeneous and heterogeneous reaction systems

The shock tube used as a high-temperature wave reactor has dominated high-temperature kinetics for more than 45 years. The nearly instantaneous heating to high temperatures, the accessible wide temperature and pressure ranges, and the diffusion-free reaction conditions are the main advantages of this technique for measuring rate co-efficients at high temperatures. In this paper some applications of the shock tube technique for kinetic studies in homogeneous and heterogeneous reaction systems will be discussed. The examples to be presented were obtained in the author's laboratory. They include thermally and photolytically induced chemical reactions, which were studied by applying different optical absorption techniques.

Preparation And Properties Of Fluorinated Amorphous Carbon Thin Films By Plasma Enhanced Chemical Vapor Deposition

AbstractFluorinated amorphous carbon films are proposed as low dielectric constant interlayer dielectrics for ULSI circuits. The films are deposited by plasma enhanced chemical vapor deposition with CH4, CF4 and C2F6 in a parallel-plate rf (13.56 MHz) reactor and a helicon wave reactor. In a parallel-plate reactor, the dielectric constant of the amorphous carbon films deposited with CH4 increases with increase in rf power. Addition of CF4 to CH4 reduces the dielectric constant to 2.1 and raises the deposition rate. However etching reaction occurs with high CF4/CH4 ratios. No film grows with only CF4. XPS measurement reveals that the F atoms are introduced into the amorphous carbon films. Helicon reactor has higher plasma density and is expected to achieve higher deposition rate for productive use. In this reactor, fluorinated amorphous carbon films without hydrogen content can be obtained with only CF4 and C2F6 gases. The growth rate of the films reaches 0.3 μ/min with C2F6 and 0.15 μ/min with CF4 at a source power of 2 kW and a gas flow rate of 100 sccm. With heating up to 300°C in a vacuum for 1 hour, the thickness of the films deposited with C2F6 does not shrink while that of films with CF4 shrinks.

Anisotropic Etching of Submicronic Resist Structures by Resonant Inductive Plasma Etching

The etching of submicronic resist structures in an oxygen plasma has been investigated in a helicon wave reactor. Systematic investigations have been conducted on the structure profile dependences on ion energy and on plasma pressure. For resist etching, the result of these investigations revealed the considerable heat transfer between the plasma species and the substrate. To obtain anisotropically etched resist structures, it was necessary to cool the wafer holder at low temperature ( -75°C) and reinforce the thermal conduction between the wafer and wafer holder. Comparison of an anisotropic process, obtained with conventional reactive ion etching (RIE), is made in terms of etch rate, sidewall passivation and surface pollution.

4479364 Sorption units and methods for their operation

The new regenerator–recuperator scheme of filtration combustion VOC oxidizing reactor is under research. Its main characteristics, such as maximum temperature of reactor, temperature of exhaust gases, NO emission and others are calculated and compared with the same characteristics of other types of reactors (co-flow filtration combustion wave reactor, counter-flow heat exchange recuperative reactor, reverse flow regenerative reactor). It is shown that the regenerator–recuperator scheme provides important advantages (wide range of flow rate, and equivalence ratio of the combustible, low temperature of the exhaust gases) compared to conventional schemes.

Continuous shock wave reactor for chemical production and reaction studies

A continuous shock wave reactor with a single instrumented shock tube was built, based on the concept of a disc rotating within a concentric ring about a shaft perpendicular to the disc's plane. The shock tube is a small tube having a square cross section, which is also a diameter of the disc. The ring contains ports connected in sequence to a process gas reservoir at low pressure, a driver gas reservoir at high pressure, driver gas outlets and product sample containers. Rotation of the disc results in successive opening and closing of these ports causing the charging of the tube with process gas, the generation of shock waves rapidly heating the process gas and of rarefaction waves cooling it, and removal of driver and product gases. The ability to produce relatively large quantities of reaction products and the small size of the installation give this device an advantage over the usual single-pulse shock tube, especially in the study of trace components in complex product mixtures.