Effect Of Oxygen Addition Research Articles

Evaluation of the effect of oxygen addition on charge carrier transport properties in single-crystal diamond growth

The effects of oxygen addition during single-crystal diamond growth by microwave plasma CVD method on crystal surface morphology and charge carrier transport properties were evaluated. Diamond single-crystals were homoepitaxially grown on (001) surface of high-pressure and high-temperature (HPHT) synthesized type IIa single-crystal diamond substrates with a fixed methane concentration of 1 % and oxygen concentrations of 0–0.8 %. Inverted pyramid-shaped pits were generated as the oxygen concentration increased. The free exciton recombination emission intensity in the cathodoluminescence spectrum reached a maximum at oxygen concentration of 0.5 %. The samples with oxygen concentrations of 0.5 % and 0.8 % showed excellent charge collection efficiency and energy resolution. On the other hand, the mobility-lifetime (μτ) product was only (7.1 ± 1.7) × 10−5 cm2/V, which is approximately 1/4 of that of the sample with 0.2 % methane and no oxygen addition.

The effects of oxygen addition on microstructure and mechanical properties of Ti-Mo alloys for biomedical application.

The effective use of oxygen as an alloying element in Ti alloys is attractive due to the reduction of production cost and the increase in strength and hardness of the alloy. Although the oxygen addition in a Ti alloy increases strength and hardness, it may induce brittleness. An appropriate combination of alloying elements and thermomechanical treatment must be clarified for the use of oxygen as an alloying element. Ti-(0, 1.0, 2.0, 3.0)Mo-(0, 1.5, 3.0)O alloys were developed, and their microstructure and mechanical properties were examined. Ti-1Mo-3O alloy exhibited fine grains of α+β two phases having the tensile strength of 1,297MPa with 15.5% for total strain at fracture. The Ti-1Mo-3O alloy has 1.5 times the tensile strength and the same total strain as the Ti-6Al-4V ELI alloy. Ti-(1.0, 2.0, 3.0)Mo-1.5O alloys also have excellent mechanical properties, with tensile strength of about 1,050-1,150MPa and a total strain of about 20%-25%. In order to develop a high strength and moderate ductility Ti-Mo alloy using oxygen as an alloying element, the microstructure should have fine grains of α+β two phases with proper volume fraction of α and β phases and specific molybdenum concentration in β phase.

Effects of oxygen addition to the fuel stream on the soot formation in an ethylene coflow partially premixed flame based on the orthogonal decoupling method

In this work, an orthogonal decoupling method based on the orthogonal design and decoupling method was used to simulate the effects of adding oxygen (O2) to the fuel stream on the soot formation characteristics in an ethylene (C2H4) coflow partially premixed flame. The dilution effect, thermal effect and chemical effect of the added O2, as well as the interaction between these effects were decoupled and analyzed. Results show that the peak soot volume fraction (SVF) in the flame decreases first and then increases as the O2 mole fraction gradually increases to 30%, and is lowest at an addition of 20%. The orthogonal decoupling calculations were performed for two O2 concentration ranges of 5%–10% and 25%–30%, and the differences on soot formation at these two ranges were found to be dominated by the chemical effects of O2 through the extremum difference analysis of the calculated peak SVF, number density of primary particle and particle aggregation degree. The chemical effect of O2 inhibits the formation of soot at an O2 addition of 5%–10%, while promotes the formation of soot at an O2 addition of 25%–30%, by affecting the inception, hydrogen-abstraction-carbon-addition (HACA) reaction, and polycyclic aromatic hydrocarbon (PAH) condensation rates of soot formation. When the O2 concentration is 25%–30%, the chemical effect of O2 promotes the soot surface growth rate and therefore increases the soot particle size, which in turn retards the complete oxidation process, leading to an increase in SVF.

Effects of oxygen addition on properties of an amorphous Co–Ta–B system

Generally, amorphous alloys with metallic luster are mechanically strong and tough, whereas they are optically opaque. In contrast, amorphous metal oxides are optically transparent, whereas they show very low fracture toughness due to their intrinsic brittleness. Introducing oxygen into amorphous alloys enables formation of multifunctional amorphous materials, which combine high strength of amorphous alloys and optical properties of amorphous metal oxides. Using this strategy, a series of amorphous thin films were developed via oxygen manipulation in an amorphous Co–Ta–B system. The effects of oxygen addition on the optical properties of the amorphous Co–Ta–B–O thin films have been investigated systematically. Optical transmittance of these thin films increases with increasing the oxygen content. Integrating the transparent Co23·17Ta9·20B16·94O50.69 thin film with Si substrate forms a bilayer structure to display various colors via a simple thin film interference effect. In addition to the optical properties, the Co24·37Ta6·96B24·99O43.69 thin film with dual-phase nanostructure show a combination of high hardness of ∼7.49 GPa and a high H/E ratio of 0.062, representing good wear resistance. Our results offer a simple means to produce mechanically strong amorphous thin films with attractive optical properties, which show potential as advanced surface coatings to meet the requirements for high hardness and decorative appearance.

Effects of oxygen addition on thermal and pollutant emission characteristics of a cylindrical furnace fueled with 1-Hexanol–biodiesel–diesel blends

This study aims to investigate the combined effects of oxygen addition to inlet air and utilization of 1-Hexanol, biodiesel, and diesel blends on the thermal and emission characteristics of a cylindrical furnace. The design of experiments was used based on the presence of three-composite fuels and the oxygen inlet flow as independent variables. The experimental tests were conducted on a cylindrical furnace equipped with a diesel burner. The results showed that the combustion temperature increased by up to 11 °C with the increase in the flow rate of oxygen addition. Moreover, the results indicated that with an increase in oxygen addition flow rate, the HC and CO emissions decreased by almost 33% and 18%, respectively. However, there was no significant effect on CO2 emissions. On the other hand, the amount of NOx emissions increased with oxygen addition flow rate by approximately 12.5%. According to the results, the increase in the percentage of biodiesel and hexanol caused an increase in NOx emissions and a reduction in CO and HC emissions. And, the fuel mixture with 50% diesel, 30% biofuel, and 20% 1-Hexanol (D50B30H20) had the maximum NOx emissions and the minimum HC and CO emissions in comparison with other fuel mixtures for all oxygen addition flow rates. The results also indicated that increasing the percentage of biofuels in the fuel mixture, along with an increase in the rate of oxygen addition, leads to a higher reduction rate of HC and CO emissions. Furthermore, oxygen flow rates higher than 5 liters per minute did not significantly affect the formation of CO2 emissions, but prevented the formation of NOx.

High‐Brightness GaN‐Based Blue Light‐Emitting Diodes Using AlON Buffer Layer on 4 In.‐Patterned Sapphire Substrate: Low‐Dislocation‐Defect Epitaxy, Growth Mechanisms, and Higher Device Performance

AlN is a common buffer layer in GaN‐based light emitting diode (LED) devices. However, application of AlN on industry‐relevant patterned sapphire substrate (PSS) causes unwanted screw dislocations in the epitaxial layer during GaN nucleation. Industry experience suggests that AlON buffer layer improves the quality of GaN epitaxial layer, but the low‐dislocation‐defect epitaxy mechanisms remain unclear. Herein, high‐brightness GaN‐based blue LEDs with the sputtered AlON buffer layer on industry‐grade four‐inch PSS is demonstrated. The effect of oxygen addition to AlN is revealed by growing GaN epitaxial layers on AlON buffer layers with different oxygen contents and testing these GaN layers in LED devices. Compared with conventional AlN, our AlON buffer layer reduces the density of screw dislocations, thereby improving the quality of the GaN epitaxial layers and the performance of GaN‐based LEDs. These insights allow the explanation of the growth mechanisms of GaN on PSS with AlN and AlON buffer layers and can guide the development of next‐generation optoelectronic technologies.

Acceleration of Isothermal ω Phase Formation by Oxygen Addition in Ti–Nb Alloys during Cooling Process

The effect of oxygen addition on the microstructure formation during cooling from the β phase in the Ti–Nb alloy was investigated. The alloy ingots of Ti–(13∼20) at%Nb–(0∼3) at%O were arc-melted. They were homogenized at 1200°C for 3.6 ks and then hot-rolled at 850°C into 1.5 mm thick sheets. The disk specimen of 3 mm diameter was heated up to β phase field at 1000°C in the differential thermal analysis apparatus. And then specimen was cooled to room temperature at a cooling rate of 20°C/min. The β → α transformation was accelerated by the oxygen addition in Ti–(13∼15) at%Nb alloys. On the other hand, the oxygen addition promoted β → isothermal ωi transformation in Ti–(16∼20) at%Nb alloys. The promoting effect increased up to 1.5% oxygen, but the effect weakened by adding more than 1.5 at% oxygen in Ti–(18, 20) at%Nb alloys. The addition of oxygen over 3.0 at%O might suppress the β → ωi transformation in Ti–20 at%Nb alloy.

Effect of oxygen addition on phase composition and activation properties of TiFe alloy

TiFe is one of the most promising hydrogen storage materials owing to its high volumetric hydrogen capacity, moderate operating temperature, and low cost. Oxygen is an inevitable impurity that affects the hydrogen storage properties of TiFe alloys. In this paper, the effect of oxygen addition on the phase composition and hydrogen storage properties of TiFe alloys is systematically investigated. We found that a high oxygen addition improves the initial hydrogen sorption of TiFe. The TiFe-O3.78 alloy achieves full activation after two ab/desorption cycles at room temperature. The high oxygen content facilitates the formation of Ti4Fe2O oxide in TiFe alloy, leading to improved activation kinetics. Moreover, due to the oxygen addition, the amount of TiFe primary phase reduces, and the corresponding hydrogen capacity degrades. Increasing oxygen content also leads to a slight increase in the hydrogenation equilibrium pressure, but almost no impact on the thermodynamics of TiFe alloy.

Effects of oxygen addition on the microstructure, phase transformations, and oxidation resistance of TiAl alloys

This study investigated the effects of oxygen addition on the microstructure, phase transformations, and oxidation resistance of TiAl alloys at 1023 K. The addition of oxygen stabilized the α (α2) phase at the expense of the γ phase and reduced the oxidation mass gains of the TiAl alloys by more than 20%. Oxide scales composed of external scattered Ti-rich oxide particles/Al-rich/Ti-rich mixed Ti/Al oxides, and internal affected zones with Al-rich precipitates were observed in all oxidized samples. The results showed that the microstructure and phase transformations of the alloys were altered by adding 1 at% oxygen. The addition of O accelerated the α → α2 chemical ordering reaction and partly suppressed the α → γ massive phase transformation. The oxidation resistance of the TiAl alloys in air at 1023 K was not significantly affected by the addition of oxygen.

Effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti–34Nb alloy

Effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti–34Nb alloy

Influence of oxygen and plastic deformation on the microstructure and the hardness of a Ti–Nb–Ta–Zr–O Gum Metal

In this paper, the Gum Metal Ti–29Nb–13Ta-4.6Zr-xO with two different oxygen contents (2200 and 4600 ppm) was prepared by high-pressure torsion (HPT) and their microstructural evolution, thermal stability, physical and mechanical properties were investigated for specimens prepared under different processing conditions. An increase in the β-phase stability at the expense of αʺ, as well as in the hardness was observed with the combined effect of oxygen addition and HPT processing. The increase in hardness was attributed to the microstructural refinement, to the creation of a high density of defects, and to the stress-induced ω-phase formation, which were all obtained due to the severe plastic deformation. Besides that, oxygen solid solution hardening provides a great increase in hardness. Vickers microhardness of approximately 400 HV was obtained for samples with higher oxygen content and deformed by HPT. The elastic modulus did not change significantly for the different oxygen levels, with values of 53–66 GPa. The typical Gum Metal properties were attained in the present paper, and they are directly related to its deformation mechanisms such as slip, stress-induced αʺ-martensite as well as reverse martensitic transformation (αʺ → β). The unique Gum Metal properties combined with the obtained increase in hardness make these two alloys very well suited for biomedical applications such as implants.

Achieving high strength and low Young’s modulus in martensitic Ti-Nb-O alloys

In this study, the effects of oxygen addition on the phase formation and mechanical behavior of martensitic Ti-Nb-O alloys with relatively low Nb contents were evaluated. The oxygen content did not change the phases formed after solution followed by water quenching and samples’ microstructures were mainly composed of orthorhombic α″ martensite. The presence of retained β and ωath phases was identified in alloys with Nb content equal or higher than 20 wt%. Hardness and compressive strength increased with oxygen addition, whereas the Nb content had a minor influence. The Young’s modulus was found to be significantly affected by Nb but not by oxygen. Accordingly, it was possible to increase the mechanical strength of the alloys while maintaining their elastic moduli at a low level.

Influence of oxygen addition on the structure, mechanical and thermal properties of CrN coating

In this study, the effect of oxygen addition on the structure, mechanical and thermal properties of CrN coatings was investigated. CrN, Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings reveal a single-phase cubic structure, and further increasing oxygen content results in the formation of a corundum structured Cr2O3 coating. An increased hardness from ~16.9 GPa for CrN to ~21.9 GPa for Cr0.50O0.07N0.43, ~27.0 GPa for Cr0.47O0.22N0.31, and finally ~28.6 GPa for α-Cr2O3 is obtained. Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings show a deferred onset temperature of nitrogen loss than CrN by ~100 °C. During annealing, the hardness value of the CrN coating decreases to ~11.3 GPa at 900 °C and then inversely increases to ~17.9 GPa at 1200 °C, while those of Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings exhibit a continuous drop to ~14.5 and ~20.6 GPa at 1200 °C, respectively. The oxidation resistance of Cr-O-N coating is closely related to oxygen content. After oxidation at 800 °C for 20 h, the oxide scales of CrN, Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings are ~0.22, ~0.16 and ~0.55 μm in thickness, respectively. In addition, the Cr2O3 coating always retains excellent mechanical and thermal properties regardless of in Ar or synthetic air.

Synergy effects of Al-V-co-doping and oxygen reactive sputtering on electrical and optical properties of ZnO films

Zinc oxide has attracted attention because of its unique properties that can be modified by doping. In this paper, we investigate the effects of oxygen addition to argon plasma during the sputtering of vanadium and aluminum co-doped zinc oxides. We find that reactive sputtering with oxygen is effective at reducing defects that degrade electrical conductivity and optical transmittance. Further, the effect of oxygen is enhanced when both aluminum and vanadium are co-doped in zinc oxide, resulting in compensation of the defects. Under an optimum condition, an electrical resistivity of 1.2 mΩcm and a 78% of transmittance were achieved.

Phase Stability and Deformation Behavior of TiZrHfNbO High-Entropy Alloys

Strengthened by Oxygen doping, the single-phase body-center-cubic (BCC) TiZrHfNbO refractory high-entropy alloys (HEAs) become strong and ductile. However, phase stability at intermediate temperature and the effects of Oxygen addition on the deformation behavior during tensile tests need to be well understood. In the present work, the phase decomposition of (TiZrHfNb)100-xOx HEAs with Oxygen doping in the range of x=0, 0.5, 1, 1.5, 2 was examined at 873 K. The formation of hexagonal-close-packed (HCP) solid-solution precipitates in submicron size, enriched with Hf, Zr and O elements, were investigated by a combination of X-ray diffraction, transmission electron microscopy and atom probe tomography. Tensile tests of alloys annealed at both 1273 K and 873 K were conducted. It was found that doping Oxygen increased the yield strength and maintained ductility for alloys annealed at 1273 K, while formation of HCP precipitates after annealed at 873 K deteriorates the plasticity significantly. To unveil the deformation behaviors, in situ synchrotron X-ray diffraction experiments were applied in the current research. The single-crystal elastic constants and shear elastic anisotropy of HEAs with and without Oxygen doping were calculated and found similar to those of “Gum Metal” Ti alloy. Yet current HEAs possess higher BCC phase stability than “Gum Metal”, and no stress-induced phase transformation was detected during deformation.

Effect of oxygen addition on the formation of isothermal ω phase in Ti-Fe alloys

The effect of the addition of oxygen on the formation of microstructure cooled from the β phase of Ti-Fe alloy was examined. The alloy ingots of Ti-(4, 5, 6, 7, 8, 9 and 10) at.% Fe and Ti-8 at.% Fe-(1 and 3) at.% O were arc-melted. They were homogenized at 1200 °C for 3.6 ks and then hot-rolled at 850 °C into 1.5-mm thick sheets. The disk specimen was fabricated and then put in the differential thermal analysis (DTA) apparatus. The disk in the DTA was heated at 1000 °C for 0.6 ks in the β phase and then cooled to room temperature at a rate of 50 °C/min. The microstructure was examined by an optical microscope after the DTA experiment. In the Ti-(7 and 8) Fe alloys the ω phase formed during cooling. The addition of oxygen in the Ti-8Fe alloy promoted the β→α transformation. Furthermore, the addition of one at.% oxygen in the Ti-8Fe alloy promoted β→ωi transformation, while the addition of three at.% oxygen suppressed the β→ωi transformation during cooling.

Deformation mechanisms and effect of oxygen addition on mechanical properties of Ti-7.5Mo alloy with α” martensite

Effect of oxygen content as an important interstitial solute on the microstructure and mechanical properties of Ti-7.5Mo alloy was investigated. With increasing the oxygen content, the yielding strength, ultimate tensile strength and Young’s modulus of Ti-7.5Mo-xO (x=0, 0.2, 0.3, 0.4, 0.5) alloys increased, while the elongation showing a decreasing tendency. Solid-solution strengthening by the oxygen atoms has been addressed as the main strengthening mechanism. Ti-7.5Mo-xO (x ≤ 0.3) alloys have been regarded with an excellent combination of high yield strength (~640 MPa) and elongation (~28%), as well as low Young’s modulus (~60 GPa). The deformation microstructure of orthorhombic-α” martensite in Ti-7.5Mo alloy was also investigated by tracking a change in the microstructure of a selected area upon tensile deformation. Deformation twins induced by 5% tensile straining was identified as {112}α”-type I twins, which had not been reported before in α”martensite in β-Ti alloys.

The Effect of Oxygen Addition on Microstructure and Mechanical Properties of Various Beta-Titanium Alloys

Simultaneously achieving high strength and low Young’s modulus is essential for implant materials due to the “stress-shielding effect”. In this work, the mechanical properties and microstructure of various beta-titanium alloys based on the Ti-Nb system with additions of Zr, Ta and Sn have been studied. Those alloys were prepared via the arc melting process. Thermo-mechanical processing (i.e., hot forging, solution treatment and cold swaging) has been performed. The alloys exhibited low Young’s modulus around 50 GPa (43 GPa was the lowest measured value) and tensile strength around 800 MPa. The tensile strength was increased via aging treatment (450°C/8 h) to 985 MPa while the modulus increased to 75 GPa. On the other hand the addition of 0.4 wt.% of oxygen seems to be more beneficial as the tensile strength reached values as high as 1225 MPa and simultaneously maintained low Young’s modulus (~ 62 GPa) and sufficient elongation (~ 8%).

Effect of oxygen addition, reaction temperature and thermal treatments on syngas production from biogas combined reforming using Rh/alumina catalysts

Dry reforming and partial oxidation of biogas were studied using 0.5wt.% Rh/Al2O3 catalysts, both in-house prepared and commercial. The effects of O2 addition on syngas yield and biogas conversion were studied at 700°C using different O2/CH4 ratios in the gas feeding stream: 0 (dry reforming), 0.12, 0.25, 0.45 and 0.50. The highest CH4 conversion, H2 yield and H2/CO molar ratio were obtained with an O2/CH4 ratio of 0.45, even though simultaneous valorization of both CH4 and CO2 could be best attained when the O2/CH4 ratio was 0.12. Increased biogas conversions and syngas yields were obtained by increasing reaction temperatures between 650 and 750°C. A detrimental influence on catalytic activity could be observed when the catalyst was subjected to calcination. Increasing the hold time of the thermal conditioning of the catalyst under inert flow altered Rh dispersion, though had no significant impact on catalyst performance in the dry reforming of methane at 700°C and 150N L CH4/(gcath). Characterization of spent samples after reaction by Raman spectroscopy revealed the presence of carbonaceous deposits of different nature, especially on the commercial (named as Rh com) and calcined (Rh calc) catalysts, though oxygen addition in the biogas feed significantly reduced the amount of these deposits. The Rh catalysts that had not been calcined after impregnation (Rh prep) did not present any noticeable characteristic peaks in the G and D bands. In particular, scanning transmission electron microscopy (STEM) images of the spent Rh prep sample revealed the presence of very highly dispersed Rh nanoparticles after reaction, of particle sizes of about 1nm, and no noticeable C deposits. Combined oxy-CO2 reforming of biogas using highly dispersed and low metal-loading Rh/Al2O3 catalysts with low O2 dosage in the reactor feed can be used to effectively transform biogas into syngas.

Effect of Oxygen Addition on the Formation of α′′ Martensite and Athermal ω in Ti–Nb Alloys

Effect of Oxygen Addition on the Formation of α′′ Martensite and Athermal ω in Ti–Nb Alloys