Effect Of Oxidation Temperature Research Articles

Influence of Oxidation Temperature on Structure and Mechanical Properties of Titanium

Surface oxidation of pure titanium was performed in the atmosphere to increase the mechanical properties. The effect of oxidation temperature (650-900°C) for 2 h on the microstructure, composition, and mechanical properties of the treated samples was investigated using X-ray diffraction, hardness tester and indentation modulus tester, respectively. The diffusion rate of oxygen in grade-2 pure Ti with different processing temperatures discussed in present research. Based on a result of the examination, the surface hardness was increased first and then decreased as the processing temperature increased. And when the processing temperature at 850°C, the surface hardness reached the maximum value. In addition, the Young's modulus of the treated samples also showed a maximum value of 198.9 GPa for a processing temperature of 850°C. An oxidation condition of 850°C is considered optimal as it provides sufficiently high hardness during practical use.

Effect of oxidation temperature on the properties of NiOx layers for application in optical sensors

Thin NiOx layers were prepared by oxidation at 400, 500 and 600 °C of metallic Ni deposited by electron beam evaporation. The bandgap of NiOx determined from optical measurements increases from 3.6 to 3.7 eV with the increase of oxidation temperature from 400 to 500°C. Higher temperature leads to larger grain sizes, 12.6 nm at 400 °C, 15.3 nm at 500 °C and 16.1 nm 600 °C. Photodiodes based on NiOx/Si heterostructure were fabricated by evaporation of semitransparent Au top contacts. The structures with NiOx obtained at 500 °C showed superior diode characteristics compared to the other two types of devices with dark current < 3.5 × 10-8 A (current density J < 3.9 × 10−4 A/cm2) for reverse biases between 0 and -2 V and forward current of 3.3 × 10−5 A (J = 0.36 A/cm2) at bias of 1.5 V. The responsivity of these devices at 0 V is between 0.85 and 0.55 A/W for wavelengths in the 365 – 635 nm range, values higher than those previously reported for self-powered NiOx/Si photodiodes. The responsivity at reverse bias of -1.5 V increases more than 60 times to values of 33, 32, 50 and 59 A/W for red, green, blue, and ultraviolet light, values among the highest reported for broadband photodetectors. The excellent properties of the photodiodes with NiOx obtained at 500 °C are the result of a higher quality of the Si/NiOx interfacial region, which leads to lower recombination rate of the photogenerated carriers.

Effect of oxidation temperature and oxygen concentration on macro characteristics of pre-oxidised coal spontaneous combustion process

Coal fire disasters occur frequently in exposed or underground coal zones or gobs, which usually triggered by pre-oxidised coal spontaneous combustion (PCSC). The thermal mass loss characteristics and thermal effects of pre-oxidised coal with the oxidation temperature and oxygen concentration were investigated. The thermogravimetry (TG) results revealed that the oxidation reaction occurred earlier for the pre-oxidised coal than for raw coal. The pre-oxidised coal had a poor ignition performance and burnout capacity than that of raw coal. In addition, the comprehensive combustion performance of pre-oxidised coal is weaker than that of raw coal, but its combustion rate and short-term combustion intensity are higher than raw coal. The differential scanning calorimetry (DSC) results indicated that the temperature at which the thermal release of pre-oxidised coal increases rapidly lags behind that of raw coal. Moreover, the maximum thermal release power and thermal release for the pre-oxidised coal were less than those for raw coal. The risk of PCSC changes with the increase of oxidation temperature, and there is a critical value of oxidation temperature. When the oxidation temperature was less than the critical value the risk of PCSC is higher than that of raw coal. Furthermore, the critical value decreases with the increase of oxygen concentration.

Microstructural degradation in the subsurface layer of the nickel base alloy 718 upon high-temperature oxidation

ABSTRACT The focus of this study is on assessing the chromium-depletion occurring in the subsurface layer associated with the formation of chromium oxide upon high-temperature exposure. As this is a critical aspect for the lifetime of many components made of nickel base alloys, a magnetic technique was developed that allowed assessing the chromium-depleted zone in a non-destructive manner. The samples made from alloy 718 were pre-oxidised in the temperature range from 700°C to 1200°C and then characterised both magnetically and by scanning electron microscopy. Analysis of the data obtained demonstrated that the magnetic measurements are capable of revealing the effect of oxidation temperature on microstructural degradation in the near subsurface layer. Specifically, analysis of the 3rd harmonic of the eddy current signal allowed inferring the oxidation temperature and the width of the chromium-depleted layer.

Functionalization of sewage sludge char by partial oxidation with molecular oxygen to enhance its adsorptive properties

Abstract This study investigates the activation of sewage sludge char through partial oxidation with molecular oxygen with the goal to increase the concentration of oxygen-containing surface functional groups and to enhance its ammonium adsorption capacity. The effects of oxidation temperature (200–350 °C), oxygen concentration (5–21 vol %) and oxidation time (30–120 min) on the degree of char oxidation are analyzed. The results obtained by thermogravimetric and elemental analysis, and Fourier Transform Infrared and X-ray Photoelectron spectroscopy corroborate the incorporation of oxygenated functional groups on the surface of sewage sludge char either at low temperature (200 °C) using air or at higher temperature (350 °C) using 5% O2 for 30 min. The oxidation of sewage sludge char hardly increases its specific surface area. The operating conditions during oxidation must be carefully controlled to avoid runaway reactions that lead to total oxidation of char. The evolution of CO and CO2 during oxidation is a good indicator of the advance of the oxidation/burn-off reactions. The ammonium adsorption capacity of sewage sludge char increases after oxidation under mild operating conditions, providing support to the idea of onsite utilization of sewage sludge as ammonium adsorbent in waste water treatment plants. This would provide a step forward towards the implementation of a circular economy.

Enhanced photocatalytic activity of titania coatings fabricated at relatively low oxidation temperature with sulfate-acid-bath pretreatment

With the purpose of enhancing the photocatalytic activity of titania (TiO2) coatings with low cost, a method of sulfuric-acid-bath pretreatment followed by simple oxidation in air has been proposed to fabricate TiO2 coatings. The effect of oxidation temperature on the crystal structure, surface morphologies and photocatalytic activity of TiO2 coatings was investigated, to figure out the suitable oxidation temperature. XRD and Raman’s results show that the phase transformation of TiO2 starts at 773 K. The surface morphologies of TiO2 coatings clearly show the porous-like structure at lower than 873 K. With raising the temperature, the photocatalytic activity of TiO2 coatings firstly increases, then decreases, and reaches the highest at relatively low oxidation temperature of 773 K.

The Effect of Oxidation Temperature on Activating Commercial Viscose Rayon-Based Carbon Fibers to Make the Activated Carbon Fibers (ACFs)

In this work, commercial Viscose (cellulosic based precursor) rayon-based carbon fibers were oxidized to make activated carbon fibers (ACFs). Carbon fibers were made from Viscose fibers in carbonization process at 1200°C. The ultimate carbon fibers possessed carbon content above 94 mass% and fiber dimension about 8 mm. These fibers were activated to make ACFs by oxidizing gas such as steam of carbon dioxide. The experiments were conducted at temperature ranged from 800°C to 900°C with carbonic steam’s flow of 3 l.min-1. The vaporous benzene adsorbability of activated carbon fibers was then measured by Mark Bell method. The adsorbability (a) and specific surface area (ABET) of ACFs were determined. The properties of the produced ACFs were investigated and analyzed by SEM and TEM imaging. The results showed that obtained fibers have maximum benzene adsorbability of 4.58 mmol.g-1 and BET surface area reached 1357 m2.g-1. These activated carbon fibers were able to use for toxic chemical prevention equipment.

Effects of oxidation temperature on microstructure and EMI shielding performance of layered SiC/PyC porous ceramics

Herein, the influence of oxidation temperature on the oxidation behavior, microstructure and electromagnetic shielding performance of layered porous ceramics has been systematically investigated. Layered SiC/PyC porous ceramics were prepared by using low-pressure chemical vapor infiltration (LPCVI) method. The oxidized SiC/PyC layered porous ceramics exhibited a negligible mass reduction of 11.94 mg·cm−3, which indicates the excellent high-temperature oxidation resistance of porous ceramics. The electromagnetic shielding performance of SiC/PyC porous ceramics did not exhibit any obvious change even after oxidation at high temperature from 900 to 1300 °C for 10 h. The SET of the layered SiC/PyC porous ceramics was 24.1, 20.0, 19.5, 19.0, 19.8 dB after oxidation at 25 °C, 900 °C, 1000 °C, 1100 °C and 1300 °C, which corresponds to a decrease of 17.01%, 19.09%, 21.16% and 17.84%, respectively. The high-temperature oxidation has rendered a more significant influence on the reflection efficiency of the layered SiC/PyC porous ceramics.

The effect of oxidation temperature on the thermoelectric performance of a plate-type thermoelectric power generator

This paper reports on the effect of oxidation temperature on the thermoelectric performance of a plate-type thermoelectric power generator. Recently, thermoelectric power generation methods have attracted considerable attention as energy harvesting technologies. Among these, a plate-type thermoelectric power generator in which an Al layer is deposited on a Fe plate has been reported. Although oxidation of the surface of the Fe plate was verified experimentally to be effective in enhancing the thermoelectric performance, the kind of oxide suitable for a plate-type generator has yet to be investigated. In this study we oxidized the surface of an Fe plate at different temperatures, and plate-type thermoelectric power generators having various oxides at the bi-metallic interface were fabricated. It was found that Fe2O3 made a large contribution to increasing the Seebeck coefficient compared with Fe3O4. The generator with a bi-metallic interface oxidized at 400 °C showed the maximum power, the value being 1.4 μW at a temperature difference of 40 °C. Furthermore, we developed a theoretical model to predict the maximum power of a plate-type generator based on solid-state physics, and the predicted values were in good agreement with the experimental ones.

Synthesis of NiO Nanotubes via a Dynamic Thermal Oxidation Process.

Nickel oxide (NiO) nanotubes were synthesized via a thermal oxidation process from Ni nanowires. The effects of oxidation temperature on the morphology, microstructures, and composition of nanowires were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show that the Ni nanowires convert initially to Ni/NiO core-shell nanowires with increasing annealing temperatures, and then to the nanotubes at the critical transition temperature of about 425 °C. Our findings provide useful information for the preparation of NiO nanotubes to meet the required applications.

The normal spectral emission characteristics of Ni-based alloys during oxidation at high temperatures

The emissivity change due to oxidation of the Ni-based alloys that are used for turbine blades in severe environment will cause large errors in radiation thermometry. In this paper, the normal spectral emissivity of three Ni-based alloys DZ125, DD6 and K465 is experimentally measured during oxidation at about 810, 914 and 998 °C in air. And the measurement wavelength varies from 1.35 to 2.35 μm. The combined standard uncertainties of the normal spectral emissivity are less than 3%. The oscillations of the emissivity are observed, and the effects of oxidation temperature, heating time and wavelength on the emissivity are investigated. The oscillations of the emissivity are produced with growth of the oxidation film by the interference effect between the direct transmission radiation and the transmission radiation after reflections by the substrate and air/film interface emitted by of the substrate. The oscillation extremums of the emissivity shift towards larger wavelengths as the oxidation process proceeds. The results show that the normal spectral emissivity increases basically with increasing temperature and decreasing wavelength except for the occurrence of the oscillations of the emissivity. The normal spectral emissivity increases rapidly at the initial heating time, and the change of emissivity becomes slow when the oxidation tends to be saturated gradually. Furthermore, the emissivity models versus heating time and wavelength are established, which fit the experimental results very well. The relative errors of the fitting models for emissivity are less than 4%.

The disclosed transformation of pre-sputtered Ti films into nanoparticles via controlled thermal oxidation

Nanoparticles of TiO2 were successfully prepared from pre-sputtered Ti films using the controlled thermal oxidation. The effect of oxidation temperature on structural, morphological and optical properties in addition to photocatalysis activity of the sputtered films was tested and explained. Analysis of XRD and EDAX elucidated the enhancement in crystallization and oxygen content with the increase of oxidation temperature. SEM depicted the formation of very fine nanoparticles with no specific border on the films oxidized at 550 and 600 °C, whilst crystallites with larger size of approximately from 16 to 23 nm have been observed for the film oxidized at 650 °C. Both optical transmission and refractive index were increased with increasing the oxidation temperature. A red shift in the absorption edge was obtained for the films oxidized at 650 °C compared to that oxidized at 600 °C. The photocatalysis tests demonstrated the priority of 600 °C nanoparticle films to decompose methyl orange (MO) more than 650 °C treated film.

Effect of oxidation temperature on physical and electrical properties of ZrO2 thin-film gate oxide on Ge substrate

The effects of oxidation temperatures on metal-oxide-semiconductor characteristics of sputtered zirconium thin films on germanium systematically investigated in an oxygen ambient. The samples were oxidized for 15min at temperatures varying between 300°C and 800°C. The sample oxidized at 500°C has demonstrated the highest electrical breakdown field of 16.6MVcm−1. The crystallinity of the film was evaluated by X-ray diffraction, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopy analyses were also performed. The crystallite size and microstrain of the films were estimated by Williamson-Hall plot analysis. Optical microscopy was used to examine the sample surfaces and high-resolution transmission electron microscopy was carried out to investigate the cross-sectional structure. GeO2 was detected in samples oxidized at temperature above 600°C. A possible thermal oxidation mechanism related to the diffusion of oxygen through the ZrO2 layer and formation of germanium dioxide has been proposed and discussed.

Transformation of Ti-bearing mineral in Panzhihua electric furnace titanium slag during oxidation roasting process

The oxidation process of Panzhihua titanium slag was investigated in this paper. According to the oxidation thermodynamics analysis of Ti-bearing minerals and iron-bearing mineral, the oxidation mechanism in the oxidation roasting process was proposed. The DSC/DTG/TG analysis of titanium slag oxidation, the effects of oxidation temperature on the mineral phase transformation, microstructure, and element distribution of the oxidized titanium slag were investigated. The results indicated that the transformation of Ti-bearing mineral into rutile was effectively increased with the increase in oxidation temperature from 600 to 1000 °C. The high oxidation temperature had a great effect on the microstructure and element distribution of the mineral phases in oxidized titanium slag. When the oxidation temperature was above 1400 °C, the titanium slag melted and TiO2 reacted with Al2O3 and MgO to form Al2TiO5 and MgTi2O5, which led to the Mg and Al contents of MxTi3−xO5(M = Mg, Al, Fe) obviously increased. The shape of rutile turned from acicular crystal to granular when the oxidation temperature was over 1000 °C, and the rutile particle grew up obviously from 1–2 μm (1000 °C) to 50–100 μm (1550 °C). The impurities in oxidized slag could be removed by pressure HCl leaching. The final rutile product with 90.06 mass% TiO2 was obtained.

Effect of oxidation temperature on the ferromagnetism of Co doped ZnO films via thermal oxidation of electrodeposited Co/Zn bilayers

Abstract Room temperature ferromagnetism (RTFM) is detected in the Co doped ZnO films, which are formed via the thermal oxidation of electrodeposited Co/Zn bilayers. The effect of oxidation temperature on the origin of RTFM is examined. Results indicate that various contents of Co 2+ dopants, Zn x Co 3−x O 4 clusters, O vacancy and Zn interstitial are achieved in the films oxidized at 400 and 550 °C. The amount of O vacancy decreases sharply with increasing oxidation temperature. This leads to the saturation magnetization of films oxidized at 400 °C is higher than that of films oxidized at 550 °C. This indicates that the effect of O vacancy on ferromagnetism is more prominent in the Co doped ZnO films.

The Effects of Oxidation Temperature on the Microstructure and Photocatalytic Activity of the TiO2 Coating

Titanium coatings were prepared on the surface of 1mm ZrO 2 balls by mechanical ball mill, then the coatings were oxidized to photocatalytic TiO 2 films at 400 ~ 600 °C. X-Ray Diffraction, Scanning Electron Microscope, Energy Dispersive Spectroscopy and Optical Microscope were used to analyze the microstructure and crystal form of the films. The photocatalytic activity of the samples was also evaluated. After that, the effects of oxidation temperature on the microstructure and photocatalytic activity of the films were discussed. The results show that the fabricated coatings are uneven, with average thickness of 60 μm. In the process of oxidation, oxygen is imported into the inner coatings by the gaps existed in the Ti coatings, which makes the Ti particles oxidize from surface to core, finally the films with TiO 2 + Ti composite microstructure are obtained. The films oxidized at 500 °C have the best photocatalytic performance with the degradation rate of methyl orange solution 79.08 %, this owing to the existence of anatase and the TiO 2 +Ti composite microstructure. The result will provide theoretical basis for the fabrication of efficient photocatalytic film. DOI: http://dx.doi.org/10.5755/j01.ms.23.2.15590

Oxidation of core–shell MoO2–MoS2 nanoflakes in different O2 ambience

Oxidation of MoO2/MoS2 core–shell nanoflakes (NFs) has been investigated in different oxidation ambients i.e. oxygen (O2) gas and its plasma. Core–shell nanoflakes are oxidized at temperatures varying from 150 °C to 450 °C and the effect of oxidation temperature on the structural and morphological changes of nanoflakes are investigated systematically. High-resolution transmission electron microscopy (TEM) images show that shell of nanoflake is oxidized with varying thicknesses and strongly depending upon the temperature and ambience. X-ray diffraction (XRD) and Raman analysis revealed the formation of MoO3 at low temperature (⩽150 °C) in O2 plasma. Whereas, in O2 gas at a relatively higher temperature (⩾350 °C). Scanning electron microscopy (SEM) results show noticeable changes in the morphology as deformation of nanoflakes after oxidation. X-ray photoelectron spectroscopy (XPS) revealed, oxidizing in O2-plasma led to multiple oxidation states of Mo (4+, 5+, and 6+) and S (2−, 6+). It is evident that the extent of oxidation of MoS2 shell is higher in plasma due to reactive species of oxygen (O+, , O*, etc), as compared to O2 gas.

Aqueous solution of Oxone as new oxidizing agent for multi-walled carbon nanotube functionalization

ABSTRACTIn this work, multi-wall carbon nanotube (MWCNT) was successfully modified using aqueous solution of Oxone as a new oxidant. The effect of oxidation temperature on various characteristics of the treated MWCNTs was also investigated. FTIR and titration analysis proved the formation of carboxyl, carbonyl and epoxide groups at the surface of MWCNTs. The concentration of the functional groups increased as the modification temperature increased. The presence of such oxygen containing groups at the surface of MWCNTs justified the long time stability of the treated MWCNTs suspensions in water and methanol. The modified MWCNTs showed higher entanglement compared to row MWCNT due to the cross-links adjacent effect of pendant functional groups. Finally, it was concluded that Oxone oxidation process destroys the structure of the MWCNTs, but not severe enough to unzip the MWCNTs.

The effect of oxidation on the mechanical properties and dielectric properties of porous Si3N4 ceramics

The effect of oxidation temperature and time on the microstructures, phase compositions, mechanical properties, and dielectric properties of porous Si3N4 ceramics was investigated in the temperature range from 900°C to 1300°C for 1h, 5h, and 24h. The weight gain measured either at lower temperature (900°C) for long time (24h) or at higher temperature (1300°C) for 1h demonstrated that the porous Si3N4 ceramics were easily oxidized under the current test conditions. Results showed that the amount of open pores, flexural strength, compressive strength, and dielectric constant all decreased with the increase of oxidation temperature independent upon the oxidation time. The oxidation product SiO2 was low-temperature quartz in mild condition (low temperature, short time) and cristobalite in severe condition (high temperature, long time). The existence of cracks on the oxide scale was due to the phase transformation of SiO2 and thermal expansion coefficient mismatch between SiO2 and Si3N4.

Effect of Oxidation Temperature on Photo-catalytic Properties of Stainless Steel Coated by Copper Oxide

Effect of Oxidation Temperature on Photo-catalytic Properties of Stainless Steel Coated by Copper Oxide