Effect Of Low-temperature Oxidation Research Articles

Effect of low-temperature oxidation and heat treatment under vacuum on the Al-Be interdiffusion process.

The oxidation of the Be/Al and Al/Be bilayer thin film systems deposited by magnetron sputtering have been studied by photoelectron spectroscopy and transmission electron microscopy. Both systems are oxidized according to the Cabrera-Mott model in the air. A Be/BeO/Al/Al2O3 structure is formed, with aluminium represented as localized nanocrystals. The thickness of the beryllium in the Al/Be system and the formed beryllium oxide is not enough to prevent the diffusion of aluminium ions under the influence of the Mott potential, and as a result, the surface layer is a mixture of beryllium and aluminium oxides. The effect of oxidation processes on the intermixing of non-interacting metals in a bilayer nanostructure has been shown for the first time. Annealing of the Be/Al bilayer leads to beryllium diffusion to the surface and the reduction of aluminium oxide, which leads to the destruction of the bilayer structure. In the Al/Be system in the range up to 200 °C, additional beryllium oxide is formed with increasing temperature, and the rest of the metallic beryllium diffuses into the aluminium layer. Based on studies, we conclude that multilayer Al/Be nanostructures have potentially low thermal stability, which requires the use of barrier layer techniques to limit interdiffusion.

The effect of low-temperature oxidation on asphaltene structure and properties during air injection

Air injection is a promising method to enhance light crude oil recovery. To effectively utilize this technology, understanding the oxidation behaviour and interactions of SARA components during low-temperature oxidation (LTO) is crucial. In this study, the SARA components of two light crude oils from the Xinjiang oilfield were characterized during LTO under air and nitrogen atmospheres, respectively. Firstly, our results revealed that the oxidation behaviour under air significantly affected crude oil stability at temperatures above 150 °C. Secondly, asphaltene component exhibited the highest oxidative activity, leading to the introduction of more oxygen and further oxidation of C–O groups and sulphoxides on the asphaltene surface. This resulted in stronger intermolecular forces among asphaltene molecules. Furthermore, the polarity characterization showed increased polarity difference between asphaltenes and resins. Structural parameters changes were observed in asphaltene aggregates, with enhanced aromaticity and accumulation of aromatic sheets after LTO reactions. Finally, these findings contribute to a deeper understanding of SARA component oxidation and interactions during LTO process, which is valuable for future air injection applications.

Effect of low-temperature oxidation on the properties of TiVN/VN multilayercoatings

An extensive study of the surface oxidation process on the properties of TiVN/VN multilayer coatings deposited by RF magnetron sputtering on Mg alloys was performed. TiVN/VN multilayer coatings with a total thickness of 660 nm and different layer numbers of 5, 11, and 33 were oxidized by annealing at 450K under partial oxygen pressure. Electronic, mechanical, and tribological properties of these coatings were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope, nanoindentation measurements, and scratch tester. The experimental results showed that the oxidation of TiVN/VN multilayer coatings leads to better performance in terms of surface roughness, hardness, and wear. The hardness of the coating increased significantly (up to 1400 HV) with the oxidation of the surface due to the release of stresses between each layer after in situ annealing. The decline of the friction coefficient after oxidation can be attributed to the formation of a self-lubricating V$_{2}$O$_{5}$ layer on the surface, the presence of which was confirmed by XPS. The findings in this work reveal a new technique for applying a better thin film coating for industrial applications of Mg alloys.

Experimental investigation and field pilot testing of air assisted cyclic steam stimulation technique for enhanced heavy oil recovery

Air assisted cyclic steam stimulation (AACSS) process is a novel technique for enhanced heavy oil recovery, which is efficient and economically attractive compared with other non-condensable gases and solvents injection-based techniques. In this study, the performance of AACSS process for an ultra heavy oil reservoir was investigated via laboratory experiments and field data analysis. The results indicate that air injection based on steam stimulation can effectively increase oil recovery in comparison with the conventional cyclic steam stimulation (CSS) process. The injected air can significantly increase and maintain the reservoir pressure, and reduce oil viscosity via flue gas dissolution and the thermal effect of low temperature oxidation (LTO) of the crude oil. The field pilot testing results of the AACSS technique in Liaohe Oilfield (Northeast China) demonstrate that AACSS can significantly increase oil production, prolong the effective production period of time, reduce water cut and the steam to oil ratio. A scoping economic study shows that the AACSS process can be more economically attractive than CSS process in terms of net present value. The AACSS technique has been effectively applied in mature heavy oil reservoirs developed by the conventional CSS, and it is also a feasible option to deep and offshore heavy oil reservoirs. [Received: January 6, 2017; Accepted: August 10, 2017]

Comprehensive investigations into low temperature oxidation of heavy crude oil

Due to the significance of low temperature oxidation (LTO) process on the subsequent oxidation reactions and oil recovery for in situ combustion (ISC), this work aimed at conducting a series of comprehensive investigations into LTO of heavy crude oil. The LTO behavior of heavy oil was analyzed by static oxidation experiments. Then the alterations in oil characteristics due to LTO were investigated through coke content measurements, flammability tests and scanning electron microscopic (SEM) observations. Additionally, the effect of LTO on thermal behavior and kinetics of heavy oil was researched using thermogravimetry (TG)/differential scanning calorimetry (DSC) technique. The results showed that the temperature played a crucial role in LTO of heavy oil. Almost no coke was deposited at 80 °C. The amount of coke deposition at 160 °C averaged 0.346 g coke/g oil, which was roughly 4.2 times higher than that at 120 °C. The oxidized oil at 160 °C possessed the most superior flammability at ambient temperature and atmospheric pressure in comparison to that at 80 and 120 °C. The surface morphologies of oxidized oil at 160 °C and its formed coke were quite rough, which boosted the subsequent combustion reactions. The results of TG/DSC unravelled that the oxidized oils were subjected to higher mass loss and exothermic effect at the fuel deposition (FD) and high temperature oxidation (HTO) stages as compared to crude oil. After the static LTO, the activation energy in the LTO and FD stages for heavy oil was increased, while that in the HTO stage was reduced. Compared with crude oil and oxidized oils, the coke deposited during the static LTO presented the highest thermal release and reaction activity in the HTO interval. This paper can provide some new insights regarding LTO mechanisms of heavy oil to rich the ISC technology.

Effect of low-temperature oxidation of light oil on oil recovery during high pressure air injection

ABSTRACTIn this research, the low-temperature oxidation (LTO) behavior of light oil was evaluated via isothermal oxidation tube experiments. Also, the core model together with nuclear magnetic resonance (NMR) analyzer was implemented to explore the effect of LTO of light oil on oil recovery during high pressure air injection (HPAI). The results indicated that the polycondensation reaction of light components (C5-C6) and intermediate ones (C7-C17) for light oil was the preferred reaction path during LTO process. The oxygen addition was the primary oxidation reaction in LTO, but the LTO reaction presented a more favorable trend for the bond scission with the oxidation degree. Because of the gas flow steering resulting from property variation of light oil and heat release determined by LTO, the total oil recovery yielded by air flooding was 8.82% higher than nitrogen flooding.

Applicable scope of oxygen-reduced air flooding and the limit of oxygen content

The mechanisms of oxygen-reduced air flooding (ORAF) and the explosion limit and the corrosion control approaches were studied based on the pilots of oxygen-reduced air flooding (ORAF) in the Dagang, Changqing and Daqing oil fields in China. On the foundation of indoor investigations and pilots, the explosion limits, oxygen reduction limits and corrosion control approaches were clarified. When the temperature of reservoir is equal to and higher than 120 °C, there is a violent reaction between oxygen and crude oil, that means the effect of low temperature oxidation would be fully taken use of to enhance oil recovery by air flooding directly; nitrogen dominated immiscible flooding with oxygen-reduced air should be applied in cases where reservoir temperature is below 120 °C with little oxygen consumption and little heat generated. The oxygen-reduced air flooding is suitable for 3 types of reservoirs: low permeability reservoir, water flooding development reservoir of high water-cut and high temperature and high salinity reservoir. In the process of development, in order to ensure safety, the oxygen reduction limits should be controlled fewer than 10%, while oxygen-reduced air can obviously reduce the corrosion rate of pipes; The surface pipelines and injection wells don't need to consider about oxygen corrosion with no water, special materials and structure of pipe or corrosion inhibitor can be applied to the surface pipelines and injection wellbores with water. Air/oxygen-reduced air is a low-cost displacement medium and it could be applied in many special conditions of low permeability reservoir for energy supplement, huff and puff and displacement, that means oxygen-reduced air flooding has become the most potential strategic technology in 20 years.

The effect of low-temperature oxidation in air-assisted steam flooding process for enhancing oil recovery

ABSTRACTAir-assisted steam flooding is a new promoting technique for enhanced oil recovery compared to the other traditional thermal recovery methods. In this study, five experiments, including one steam flooding experiment, three combined steam–air flooding experiments, and one combined steam–N2 flooding experiment were studied, under the conditions of 180 °C and back-pressure valve of 8 MPa, with sand-packed model. The volume fraction of mixed gas in these four combined steam–air (or N2) flooding experiments were 80% steam+20% air, 60% steam+40% air, 40% steam+60% air, and 60% steam+40% N2, respectively. The experimental results showed that air-assisted steam flooding could enhance the oil displacement efficiency when the volume fraction of air and steam was in a certain number, and the optimal condition is 60% steam+40% air. Furthermore, water cut curves and saturate, aromatic, resin, and asphaltene (SARA) analysis results also demonstrate that the low-temperature oxidation reaction in air-assisted steam flooding process advantageous to profile control of generating high viscosity “PLUG” to seal high-permeability channel in reservoir.

Effect of Low-Temperature Oxidation and Oxynitriding on the Fretting Corrosion of VT22 Titanium Alloy

We have investigated the influence of oxide and oxynitride layers, formed at the stage of aging (T = 620°C, t = 7 h), on the fretting resistance of VT22 titanium alloy (Ti–5Al–4.75Mo–4.75V–1Cr–1Fe) for the optimization of phase-structural state of the modified layer. It has been found that one can ensure the greatest fretting resistance in the couple VT22 alloy vs. D16T alloy by combining oxynitriding with the application of a layer of VAP-2 (MoS2) antifriction coating. As a result, the adhesion component and seizure decrease substantially. To enhance the fretting resistance of hot-heading bolts of VT22 titanium alloy, produced by the technology of thermomechanical treatment, developed at the Institute for Physics of Metals, we have proposed a technological scheme of surface modification (low-temperature oxynitriding), combined with aging in a united technological cycle.

Effect of low-temperature oxidation on the pyrolysis and combustion of whole oil

Abstract Low-temperature oxidation (LTO) of the Fosterton crude oil mixed with its reservoir sand has been investigated in a tubular reactor. Reservoir sand saturated with 15 wt% of crude oil (20.5° API gravity) was subjected to air injection at low-temperature (220 °C) for a period of time (17 h and 30 min), resulting in the formation of an oxygenated hydrocarbon fuel. The vent gases were analyzed for the content of CO, CO 2 , and oxygen and the residue was analyzed to determine the elemental composition and calorific value. The presence of LTO region was verified from the values of apparent H/C ratio. In addition, thermal behavior and combustion kinetics of the residue was investigated using thermogravimetric analysis (TGA). TG involves both non-isothermal and isothermal analysis and kinetic data was derived from isothermal studies. The general model for n th order reaction was used to obtain the kinetic parameters of the coke oxidation reaction. The activation energy, frequency factor and order of the reactions were determined using the model.

0749 メタノールポート噴射によるディーゼル燃焼の予混合化(S41-2 燃焼制御と排出物低減技術(2),S41 燃焼制御と排出物低減技術)

Methanol port injection can retard the ignition timing in premixed diesel combustion with suppression effect of low temperature oxidation, and smooth premixed combustion neat top dead center is established. However, with increasing in quantity of diesel fuel, a required quantity of methanol to suppress the low temperature oxidation increases and the high temperature oxidation becomes rapid due to higher concentration of premixed methanol and diesel fuel. In the case of this experiment as the injection timing of diesel fuel is fixed at 40℃A BTDC, the maximum BMEP is limited at 0.25MPa due to knocking without methanol. The combination of methanol injection and EGR can expand the maximum BMEP to 0.55MPa and realize smokeless and low NO_x combustion in this range.

Effect of low temperature oxidation on dielectric properties of mercury sensitized photo-deposited silicon nitride films

Low temperature thermal oxidation of mercury-sensitized photo-CVD deposited silicon-rich silicon nitride films has been carried out to obtain high quality silicon oxynitride films with less incorporated hydrogen. The absence of Si H and N H stretching mode indicates that the incorporated hydrogen in these bonding forms is a few atomic percent, below the detection level of Fourier transform infrared spectroscopy (FTIR). X-ray photoelectron (XPS) studies suggest that oxygen is mainly incorporated in the film in the form of N (SiO) x . No significant change in the relative contributions from the Si 3N 4 network to the overall N 1s peak takes place as a result of oxidation, but there is a decrease in the unreacted silicon from 15.3% to 5.5%. The interface electronic state densities, flat band voltage, fixed insulating charges and leakage current are reduced after oxidation, indicating an improvement of the electrical properties of the oxidized film.

Effects of low-temperature oxidation on natural remanent magnetization of Chinese loess

This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200°C, (1) H c and H cx significantly decrease while M rs and M s remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTO). This CRM can be sufficiently attenuated or even removed by the reducing process between 100 and 200°C during the thermal treatment and has no apparent harmful effects on the characteristic remanent magnetization (ChRM) between 300 and 500°C.

Robustness of ultrathin aluminum oxide dielectrics on Si(001)

The stability of Al2O3 films during thermal processing will help determine their usefulness as an alternative gate dielectric for advanced complementary metal-oxide-semiconductor devices. We used medium energy ion scattering and atomic force microscopy to examine the degradation of ultrathin Al2O3 layers under ultrahigh vacuum annealing and the effects of low-temperature oxidation. No degradation is observed at 900 °C, but voids appear at higher temperatures. Growth of interfacial SiO2 takes place during low-pressure oxidation at 600 °C, which may limit the capacitance of extremely thin structures.

99/02372 Effect of low-temperature oxidation of coal on hydrogen-transfer capability

99/02372 Effect of low-temperature oxidation of coal on hydrogen-transfer capability

Effect of low-temperature oxidation on the remanence properties of titanomagnetites.

Changes in remanent magnetization and hysteresis parameters associated with low-temperature oxidation have been investigated using x=0.3, 0.5 and 0.7 synthetic titanomagnetite samples and natural submarine basalts. The intensity of remanence and the median destructive field (MDF) of TRM decreases with increasing oxidation. As oxidation proceeds, the intensity of CRM increases and its MDF decreases, except for x=0.7 titanomagnetite samples, which show maximum intensity and MDF around 0.6 of oxidation state (z). The intensity and stability of CRM become almost comparable to those of TRM in a high oxidation state. Saturation magnetization (Js) decreases with increasing oxidation and in a fully oxidized state Js is about 60% of initial values. The saturation remanence of titanomagnetite samples is almost constant until z-0.6 and tend to decrease as z increases further. The coercive force and coercivity of remanence decrease for x=0.3 and 0.5 samples monotonically with increasing z, whereas those for x=0.7 samples show maximum values for oxidation states of about 0.6. The correlation is not good between oxidation state z and the NRM intensity of submarine basalts, while the NRM becomes more stable with increasing low-temperature oxidation. Changes exhibited by DSDP samples against AF demagnetization show almost the same tendency for MDF of CRM for the x=0.7. However, other parameters are not always consistent with those of synthetic samples.

The effect of low temperature oxidation on the remanence of TRM-carrying titanomagnetite Fe 2.4Ti 0.6O 4

Fine grain (∼ 0.1 μm) synthetic Fe 2.4Ti 0.6O 4 (TM60) was given a thermoremanence (TRM) in a field of 35 A m −1 prior to oxidation in air at temperatures in the range 120–300°C, also in the presence of a magnetic field. Only a small fraction of the moment (∼ 10%) was transported into the ambient field direction. The dominant feature was a fall in intensity to ∼ 50% of the initial TRM as the degree of oxidation, z (0 < z < 1), increased to a value of ∼ 0.4, followed by only a further small decrease as z rose to ∼ 0.8. The fall is too large to be accounted for as being due to the change in the intensity of individual grain moments due to the fall in spontaneous magnetization with composition. A redistribution of grain moments due to unblocking of the initial directions is also ruled out as making a significant contribution to the fall in remanence. The observed effect can be plausibly modelled as being due to the growth of a high permeability mantle which screens the residual moment of a maghemitized grain. The mantle is formed when high concentration gradients near the surface cause local catastrophic failure of the crystal so that the grain becomes surrounded by a cracked and split layer. As further gradual oxidation takes place at the surface by addition of oxygen and growth of new crystal, it is hypothesized that the porous mantle is gradually reclaimed by the grain and the screening effect reduced. This is consistent with the final observed remanence at high oxidation levels, which can be accounted for in terms of only the composition-dependent change in spontaneous magnetization. The implication of these results for the magnetization of the submarine crust is discussed.

Consequences of the maghemitization on the magnetic properties of submarine basalts: synthesis of previous works and results concerning basement rocks from mainly D.S.D.P. Legs 51 and 52

This study attempts to point out the effects of low temperature oxidation on the magnetic properties of oceanic basalts. To evidence the maghemitization effect in terms of chemical change alone, we tried to keep constant both the concentration and the grain size of the magnetic minerals. This study bears essentially on basaltic samples drilled at Site 417A and 417D during the D.S.D.P. Legs 51 and 52, but also includes other available data. The concentration changes were neutralized either by counting the magnetic oxides with a microscope or by normalizing a magnetic parameter to another one which similarly varies upon maghemitization; for the grain size, we selected magnetic criteria that seem the best to represent the magnetic domain state configuration of the titanomagnetite; thus, we chose to work with constant ranges of both H cr/ H c and J rs/ J s values. The magnetic minerals at Site 417A and 417D are titanomagnetites displaying varying maghemitization degrees, but whose original composition varies little around x = 0.55, including a roughly constant amount of minor elements (δAl ∼ 0.08 and δMg ∼ 0.04 ions per formula unit). Therefore, it was assumed that the Curie temperature rise, reliably represents the maghemitization increase. The main results are the following ones: the saturation induced magnetization J s continuously decreases by a factor of two to three during maghemitization. Consequently, this process can actually be considered to be the main cause of the decrease in the magnetic anomalies amplitude when going away from the sea-floor spreading axes. The other magnetic parameters are grain size dependent and appear to evolve in a roughly opposite way in the fine-grained (SD + PSD) and in the coarse-grained (PSD + MD) basalts. The initial susceptibility first slightly decreases then increases in the former case, while continuously decreasing in the latter. The evolution of the coercive force parameters is opposite to the susceptibility's in both groups. These results are in general good agreement with theoretical predictions and, for the fine-grained basalts, with results obtained from synthetic substituted SD titanomaghemites. However, contrary to expectations, we did not find any change in the magnetic viscosity with maghemitization. It seems rather that the viscosity is mainly controlled by the magnetic domain structure and microstructures in the titanomagnetites, being generally negligible in the fine grained basalts (pillows), and significant in the doleritic basalts. This study shows that, even if maghemitization slightly alters the reliability of fine grained basalts as palaeomagnetic recorders, these rocks still remain the main source of the oceanic magnetic anomalies; alternatively, due to their significant magnetic viscosity, the doleritic basalts contribute little to the anomaly pattern, whatever their maghemitization degree.

Effect of low-temperature oxidation on time-resolved pyrolysis mass spectra of Hiawatha coal

Effect of low-temperature oxidation on time-resolved pyrolysis mass spectra of Hiawatha coal

Inversion electron mobility in Si−SiO 2 structures oxidized at low and high temperatures

By measuring the inversion currents, two types of Si−SiO 2 structure are studied with the silicon dioxide grown in dry oxygen (H 2 O below 1 ppm) at two temperatures (850°C and 1050°C). Inversion electron mobility and charges at the Si−SiO 2 interface for both types of oxide are strongly influenced by the oxidation temperature. The degrading effect of low temperature oxidation is explained by a higher level of strain at the Si−SiO 2 interface. It is shown that the low temperature post-oxidation N 2 anneal is insufficient and the electrical properties of low temperature oxide samples are inferior to those of the high temperature oxides.