Showing papers on "Wet oxidation published in 1990"

Wet oxidation of GeSi strained layers by rapid thermal processing

Abstract: A cold‐wall rapid thermal processor is used for the wet oxidation of the commensurately grown GexSi1−x layers on Si substrates. The rate of oxidation of the GexSi1−x layer is found to be significantly higher than that of pure Si, and the oxidation rate increases with the increase in the Ge content in GexSi1−x layer. The oxidation rate of GexSi1−x appears to decrease with increasing oxidation time for the time‐temperature cycles considered here. Employing high‐frequency and quasi‐static capacitance‐voltage measurements, it is found that a fixed negative oxide charge density in the range of 1011– 1012/cm2 and the interface trap level density (in the mid‐gap region) of about 1012/cm2 eV are present. Further, the density of this fixed interface charge at the SiO2/GeSi interface is found to increase with the Ge concentration in the commensurately grown GeSi layers.

Effects of oxidation conditions on electrical properties of SiC‐SiO2 interfaces

Abstract: Electrical properties of metal‐oxide‐semiconductor (MOS) devices fabricated on 3C‐SiC single crystalline films on (100)Si substrates have been examined by capacitance‐voltage method and deep level transient spectroscopy. The electrical properties such as carrier concentration, interface states, fixed oxide charge and deep traps are strongly related to the oxidation ambient and temperature. It has been found that the interface state density of the order of 1010 cm−2 eV−1 can be achieved by wet oxidation at 1000 °C. The influence of preferential oxidation of antiphase grain boundaries is considerable on the carrier concentration and the interface state density in the case of wet oxidation. From a practical point of view, the wet oxidation is concluded to be superior to the dry oxidation because of the lower densities of fixed oxide charge, interface states, and deep traps.

Surface modification of carbon fibres by plasma polymerization

Abstract: One of the main features for fibre reinforcement of a polymer matrix is found to be the improvement of interfacial adhesion. Therefore, a variety of surface treatments and coating techniques have been elaborated. For example oxidation of carbon fibre surfaces with gaseous or liquid oxidizing agents /1–2/ allows the activation of the surface by introduction of chemical groups containing oxygen. Such functional groups improve interfacial adhesion between the fibres and the matrix. But as a disadvantage of gaseous oxidation a substantial decrease of tensile strength due to damage of the fibre surface is known whereas wet oxidation results in treatment times of several hours.

The mechanism of epitaxial Si‐Ge/Si heterostructure formation by wet oxidation of amorphous Si‐Ge thin films

Abstract: Epitaxial Si‐Ge/Si heterostructures have been formed from amorphous Si0.86Ge0.14, Si0.7Ge0.3, and Si0.56Ge0.44 films which were deposited at a vacuum of 10−7 Torr, followed by a wet oxidation process. The presence of an initial native oxide precluded solid phase epitaxy under standard annealing conditions, but epitaxy could be achieved by the use of wet oxidation. The samples were oxidized for various times at 900 °C and examined in reflected electron diffraction, ellipsometry, and cross‐sectional and plan‐view transmission electron diffraction. The formation of the epitaxial layer has been examined, and an epitaxial growth model is suggested.

Oxidation resistance of silicon nitride ceramics with various additives

Abstract: Five silicon nitride ceramics with various additives were evaluated for their oxidation resistance at 1300 ° C in flowing dry and wet air. In a dry atmosphere, the oxidation of all types of Si3N4 except one proceeded in two stages with different reaction rates nearly following the parabolic law. In a wet atmosphere, all types showed a linear relationship between weight gain by oxidation and water varpour content. The water vapour in the atmosphere slightly accelerated the oxidation. The influence of oxidation on room-temperature strength was complex, but there was no observed distinguishable difference of the effect on the flexural strength between dry and wet oxidation.

Method for purification of waste water

Abstract: A method for the purification of waste water by the use of a heat-exchanger type reaction vessel composed of a plurality of inner tubes and a shell defining jointly with the outer peripheries of the inner tubes a passage for the flow of a heat transfer medium, which method comprises passing said waste water through said inner tubes and, at the same time, feeding a molecular oxygen-containing gas to the flow of said waste water thereby establishing contact between said waste water and said feed gas and consequently effecting wet oxidation of the impurities present in said waste water.

Carbon Fibre Surfaces and Their Analysis

Abstract: Chemical analysis of C-fibres after controlled surface treatment (wet oxidation and anodic oxidation)have been performed by total oxygen and nitrogen analysis, organic blocking methods, thermal desorption with in situ gas analysis, ESCA and IGC.

Treating apparatus for waste water

Abstract: PURPOSE:To reduce running cost for the treatment of waste water by constituting a treating apparatus of a wet oxidation tower, an insolubilizing tank for insolubilizing P by adding an insolubilizing agent for P to the treated water of the wet oxidation tower, and a membrane separator for separating the reaction liquid from the insolubilizing tank for P through a precision filtration membrane or ultrafiltration membrane. CONSTITUTION:Waste water contg. materials to be oxidized and P from a feed liquid feeding line a is fed to a wet oxidation tower 1, where it is heated and pressurized to oxidize the material to be oxidized in the waste water, and the materials to be oxidized are decomposed to gaseous CO2, N2, and water. The gas/liquid mixture is transported to a gas/liquid separation tower 3, and treated water decomposed by the oxidation in the tower 3 is transported to an insolubilizing tank 10 for P, where it is mixed and stirred with slaked lime and a pH adjusting agent in a mixing and stirring zone 12. Thus, the P in the treated water is insolubilized. The treated water contg. the insolubilized P overflows a top of a separating wall 11 and is introduced into a pump pit 13, then fed to a membrane separation device 20 hosing an ultrafiltration membrane therein through a line 19. Permeated water of the membrane separation device is discharge out of the system. Thus, the frequency of washing in the membrane separation device 20 is reduced.

Soil recovery by wet oxidation

Abstract: The principle of wet oxidation is intended for the removal of different pollutants from soil. It is in particular well suited for organic contaminants but also certain metals may be removed. Aiming at a continuous pipe autoclave operation a series of bench scale experiments have been carried out. Except for chlorinated cyclic hydrocarbons organic material is oxidized to CO2, H2O and small biodegradable molecules. Oxidizable metals are soluble in alkali to a higher or lesser degree. It appears that the method is excellent for the removal of arsenic.

Comparison of two sample oxidation methods for quantitative measurement of 12c and 14c in plant and soil

Abstract: Two methods for determining total C and 14C in plant and soil were compared. One method involved wet oxidation of samples in concentrated acid and measuring evolved 12/14CO2 captured in NaOH. The other method oxidized samples in an induction furnace, measured total CO2-C by thermal conductivity, then 14CO2-C collected in a NaOH solution. Over a range of carbon contents and including both plant and soil samples, the wet and dry oxidation methods were highly correlated (r2 = 0.99) and the slope of the regression wet on dry methods (±SE) was 1.00 ± 0.01 and 1.05 ± 0.01 for total-C and 14C, respectively. However, the dry oxidation method may not be as accurate as the wet method for soil samples especially at low levels of C, less than 5 mg C g−1 sample. Key words: Total carbon, carbon-14, high-temperature induction furnace, acid digestion

Technology Evaluation for Treatment/Disposal of TNT Red Water

Abstract: : The U.S. Army is continuing their investigation of potential processes for treating or disposing of the process waste stream (red water) resulting from TNT production and purification. Thirty technologies for treating red water were proposed for evaluation. The preliminary evaluation used a decision tree to determine the potential of each process to provide a technically, economically, and environmentally acceptable method for disposing of waste products from the purification of crude TNT. After the preliminary evaluation, 14 technologies were identified for secondary evaluation. The secondary evaluation used several criteria and a point assessment scale to identify the following four processes for further evaluation: (1) Wet air oxidation; (2) Circulating-bed combustion; (3) Slagging rotary kiln; and (4) Submerged combustion. Wet air oxidation involves oxidation with air or oxygen at temperatures between 175 and 327 C and pressures between 2,069 to 20,690 kilopascals. Circulating bed combustion involves thermal treatment of wastes at temperatures between 800 and 1000 C (1472 and 1832 F). Incineration by slagging rotary kiln is a process in which wastes are incinerated in a rotary kiln at temperatures greater than those used in standard rotary kilns. The submerged combustion process is similar to the slagging rotary kiln in that higher temperatures are maintained to melt the salts and to produce a slag that encapsulates the ash constituents and thus exhibits greater resistance to leaching.

Wet oxidation treatment of organic waste water

Abstract: PURPOSE:To efficiently treat even the malodorous gas generated in a system by introducing the malodorous gas as a part of the oxygen-containing gas supplied to a wet catalytic oxidation process. CONSTITUTION:High concn. malodorous gas is generated in the upper apace 1a above the liquid level in a storage tank 1. The malodorous gas compressed along with oxygen-containing gas such as air by a compressor C to be introduced into a wet catalytic oxidation tower 2 is perfectly oxidized and decomposed along with a raw solution. Therefore, exhaust gas has no malodor. In treatment, the malodorous gas can be treated efficiently, safely and perfectly without being affected by the concn. of the malodorous gas or the kind of a malodorous component and there is no fear of secondary public nuisance. Further, treatment cost is extremely low.

Purification of waste water

Abstract: PURPOSE:To effectively purify waste water by passing waste water through the inner pipe of a heat exchanger type reactor while allowing a heat transfer medium to flow along the outside of said inner pipe and supplying molecular oxygen-containing gas to the flow of waste water to subject impure substance to wet oxidation. CONSTITUTION:The waste water sent from a line 13 is supplied by a pump 7 to be preheated by a heat exchanger 5 and introduced into a heat exchanger type reactor q to be allowed to flow through the inner pipe 11 thereof along with the air from the line 14 raised in pressure by a compressor 6 and waste water having a certain COD (Cr) concn. is subjected to wet oxidation reaction and the generated heat of reaction is absorbed by the heat transfer medium recirculated by a recirculation pump 3 to be recovered by cooling water in a heat exchanger 4. After the water treated in the reactor 1 is cooled by a heat exchanger 5, said waste water is separated into harmful gas and water by a gas-liquid separator 8. By this method, the waste water containing harmful oxidizable org. or inorg substance being a COD component is subjected to wet oxidation in the presence of molecular oxygen to convert said substance to harmless carbon dioxide, water and nitrogen and can be purified effectively.

Rapid Thermal Oxidation of GeSi Strained Layers

Abstract: A cold-wall rapid thermal processor is used for the oxidation of commensurately grown GexSi1−x layers on Si substrates. It is shown for dry oxidation that the oxidation rate of GeSi is the same as that of Si. The dry oxidationrate of GeSi is independent of Ge concentration (up to 20 % considered in this study) in the GeSi layer. For wet oxidation, however, the rate of oxidation of the GexSi1−x layer is found to be significantly higher than that of pure Si, and the oxidation rate increases with the Ge concentration in GexSi1−x layer. Employing highfrequency and quasistatic Capacitance-Voltage measurements, it is found for a thin oxide that a fixed negative oxide charge density in the range of 1011 – 1012/cm2, and the interface trap level density (in the mid-gap region) of about 1012 /cm2.eV are present. Further, the density of this fixed oxide charge at the SiO2 /GeSi interface is found.to increase with the Ge concentration in the commensurately grown GeSi layers.

High Pressure Oxidation of Strained Si1−xGe Alloys

Abstract: Thermal passivation of Si1-x Gex using high pressure (10,000 psi) oxidation was studied. Alloys of Si1-xGex (with x=5.4, 11.6, and 17 at. %) approximately 200 nm thick were oxidized using two processes: (i) dry oxygen at 10,000 psi at a temperature of 550°C and (ii) conventional, 1 atm steam at 800°C. The wet oxidation conditions were chosen to produce an oxide thickness comparable (=100 nm for xGe=11.6 at. %) to that obtained during high pressure oxidation at 550°C. Auger sputter depth profiling (AES), X-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy (TEM) were used to characterize the as-grown oxides. XPS studies reveal that high pressure oxides formed from all three of the alloys of Si1-xGex have greatly enhanced incorporation of Ge compared to those grown to a similar thickness under wet atmospheric conditions. We report that a significant benefit of this increase in Ge incorporation is the minimization of Ge enrichment near the oxide/Si1-xGex interface. Cross-sectional TEM images reveal a 30 nm thick Ge-rich band at the wet oxide/alloy interface and a dramatically thinner band (<5 nm) present at the oxide/alloy interface produced by high pressure oxidation. For the atmospheric oxidation samples, interfacial misfit dislocations were observed at the alloy/substrate interface indicating that the film relaxed during oxidation. In contrast, the high pressure samples showed no interfacial defects after oxidation.