Effect Of Oxide Formation Research Articles

Effect of Oxidation Behavior of (Nd,Dy)-Fe-B Magnet on Heavy Rare Earth Extraction Process

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the LME p rocess, Nd i s completely e xtracted a fter 6 h, w hile D y remains as D y2Fe17 and Dy-oxide. Because the decomposition rate of Dy2Fe17 is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.

Microstructural measurement and artificial neural network analysis for adhesion of tribolayer during sliding wear of powder-chip reinforcement based composites

The influence of powder-chip based reinforced LM6 aluminum alloy fabricated by a consolidated effect of stirring and squeeze process in the semi-solid stage is reported for wear properties. Effect of oxide formation on the worn surfaces due to the processing was noticed and experimental results showing that powder-chip based reinforcement with semi-solid slurry affects and gave excellent resistance against the adhesive wear. Evidences of protective tribo-layers observed from the worn surface investigation, profilometer analysis, EDS and XRD results which provides an appropriate explanation for the drop in the wear rate in alloys. Specific wear rate reduction due to the effect of oxides in mixed tribolayer has been studied by artificial neural network (ANN) with two stage nested analysis which reflects only 1.11% Mean Square Error as compared to experimental values. This model provides better understanding to identify influencing parameter for huge variable set of processing and validate with sufficient accuracy.

Surface/interface-related optical properties in Si nanodisks fabricated by neutral-beam etching using bio-templates

The authors study surface/interface-related optical properties in Si nanodisks (NDs) fabricated by neutral-beam etching using bio-templates. Photoluminescence (PL) spectra and the transient properties are compared between different barrier materials of SiO2 and SiC. The PL spectral shape depends on the barrier material, indicating effects of oxide formation and/or oxygen atoms on the surface of the Si ND. The transient PL shows nanosecond-scale transition of carriers in surface-related quantum states in the ND. Temperature dependences of the PL intensity show that the activation energy responsible for the electron escape from the Si-ND at near room temperature in the case of SiC barrier agrees well with the conduction band offset, whereas that in the case of SiO2 barrier is significantly lower than the expected offset. The latter discrepancy suggests that the electronic band structure at the interface of Si-ND/SiO2 can be largely affected by dielectric screening due to oxygen atoms in the SiO2.

Alloy 182/低合金鋼溶接境界部でのき裂停留挙動に及ぼす酸化物形成の影響

本研究は，高温高圧純水環境下におけるAlloy 182/低合金鋼境界部でのき裂停留メカニズムを明らかにすることを目的とした．試験片はAlloy 182を低合金鋼に肉盛溶接したものを使用した．試験温度288℃，圧力8.0 MPa，入口側導電率10 μS/m以下，溶存酸素濃度8 ppmのオートクレーブ中で行ったCBB試験の結果より，Alloy 182側で発生・進展し溶融線まで達したき裂はすべて低合金鋼側で球状の酸化物を形成し，LAS上でのき裂伝播は認められなかった．CBB試験後，Alloy 182厚さと酸化物の大きさの関係を分類したところ，形成した酸化物の大きさはAlloy 182厚さが厚いほど大きくなった．その原因として，Alloy 182及び低合金鋼の電位差による galvanic 効果が考えられた．

Effects of oxide formation around core circumference of silicon-on-oxidized-porous-silicon strip waveguides

We have studied the effect of oxidation on the propagation loss and surface roughness of silicon-on-oxidized-porous-silicon strip waveguides fabricated using proton-beam irradiation and electrochemical etching. A thin thermal oxide is formed around the core of the waveguide, enabling the symmetric reduction of core size and roughness on all sides. Significant loss reduction from about 10 dB/cm to 1 dB/cm has been obtained in TE and TM polarizations after oxidation smoothening of both the bottom and the sidewalls by 20 nm. This corresponds well with simulations using the beam-propagation method that show significant contributions from both surfaces.

Investigation into CO2 laser cleaning of titanium alloys for gas-turbine component manufacture

This paper reports results of the investigation into the feasibility of using a CO2 laser technology to perform critical cleaning of gas-turbine aero-engine components for manufacture. It reports the results of recent trials and relates these to a thermal model of the cleaning mechanisms, and describes resultant component integrity. The paper defines the experimental conditions for the laser cleaning of various aerospace-grade contaminated titanium alloys, using a continuous wave CO2 laser. Laser cleaning of Ti64 proved successful for electron beam welding, but not for the more sensitive Ti6246. For diffusion bonding the trials produced a defective standard of joint. Effects of oxide formation is modelled and examined experimentally.

Oxygen Reduction Kinetics in Low and Medium Temperature Acid Environment: Correlation of Water Activation and Surface Properties in Supported Pt and Pt Alloy Electrocatalysts

Kinetics of oxygen reduction reaction on supported Pt and several Pt alloy electrocatalysts (PtCo/C and PtFe/C) have been investigated in terms of the effect of alloying on the initiation and extent of surface oxide formation (water activation: xH2O + Pt*(M) → (M)Pt−[OH]x + xH+ + xe-). For this, a systematic RRDE investigation has been conducted in trifluoromethane sulfonic acid (TFMSA) as a function of concentration (in the range 1 to 6 M) which corresponds to a change in mole ratio of water/acid from 50:1 in 1 M to 4:1 in 6 M TFMSA. This change in relative amount of water in the various concentrations can also be indirectly correlated to the relative humidity in an operating PEM fuel cell. The scope of this effort was (a) to confirm the shift and lowering of water activation on supported Pt alloy electrocatalysts relative to Pt at lower concentrations (1 M); (b) to compare the inherent activity for ORR on supported Pt and Pt alloy nanoparticles without the effect of oxide formation via activation of wa...

The effect of oxide formation on bistability in CO oxidation on Pt

Kinetics of CO oxidation on Pt is bistable both under UHV conditions and at atmospheric pressure. In the former case, the bistability can be explained by using the established reaction scheme, including reversible CO adsorption, dissociative O 2 adsorption, and reaction between adsorbed CO and O. Also at higher pressures, this model accounts well for the low-reactive (CO-dominated) regime. However, in the high-reactive (oxygen-rich) regime, the kinetics may be influenced by surface oxide formation at the higher pressures. Our present Monte Carlo simulations illustrate what may happen when oxide formation and removal occur with participation of gas-phase O 2 and CO molecules, respectively. Specifically, we show that these relatively slow steps may control the reaction rate in the high-reactive state. In this case, the hysteresis loop is found to be qualitatively similar to that predicted by the conventional reaction scheme, but the CO 2 formation rate in this state is appreciably lower. These predictions are in qualitative agreement with the results of recent STM studies of CO oxidation on Pt(110) at atmospheric pressure.

The influence of phase transformations and oxidation on the galling resistance and low friction behaviour of a laser processed Co-based alloy

The effect of oxide formation on the tribological properties of a CO 2-laser processed Co-based material (Stellite 21) was investigated under high-load sliding conditions in air and in an oxygen free environment. The tests were carried out by sliding two identical specimens against each other in a load-scanning test. A friction coefficient at a level of about 0.20 was observed for both test environments. However, the wear of the Co base material is accelerated when the sliding is performed in an oxygen free environment. The friction level appears to be controlled by the shearing of hcp {0 0 0 1} planes rather than by the presence of an oxide layer.

Effect of Oxidation and Plume Formation on Low Power Nd-Yag Laser Metal Interaction

The effect of oxide formation and plume formation on laser energy absorption by metallic targets has been studied. The change in directional-hemispherical spectral reflectance of metallic targets during single-shot Nd-Yag laser pulse irradiation was measured using an integrating sphere under controlled environments of both oxygen and argon gas. The spectral transmittance of the plume formed over the targets was also measured using a He-Ne probe laser. The metal targets studied included A16061, Cu, 304 stainless steel, and low-carbon steel. Results obtained show that once a target is hot enough to form a vapor plume, in either argon or oxygen, absorption by the plume significantly limits the amount of laser energy available for absorption at the target surface. Prior to plume formation, the amount of laser energy absorbed by the target is determined by the target surface optical properties. Under the conditions of the present study (incident laser flux of the order of 106 W/cm2 over 0.5–1.0 ms), in the case of absorbing metals (αλ>0.3), such as stainless and low carbon steel, the intrinsic absorptivity of the metal is high enough that the effect of ambient gas (oxygen or argon) on absorptivity is insignificant. In the case of nonabsorbing metals (αλ<0.3), such as Cu and A16061, the intrinsic metal absorptivity is low enough that the ambient gas does have a significant effect on the target absorptivity. The formation of an oxide layer that occurs in an oxidizing environment generally has the effect of increasing the target absorptivity. The relative magnitude of the absorptivity enhancement due to oxide formation depends on the respective absorptivities of the oxide and metal. For metals that form oxides that are intrinsically absorbing in the solid state, such as Cu2O or CuO, the enhancement in absorptivity due to oxide formation can be as much as an order of magnitude. For metals that form oxides that are intrinsically nonabsorbing in the solid state, such as MgO or Al2O3, the enhancement in absorptivity due to oxide formation is more modest but still significant (40 percent). The enhancement in absorptivity in the latter case (MgO or Al2O3) is postulated to be associated either with a thin, absorptive, transition region composed of a mixture of metal and substoichiometric solid oxide just below target surface or with the melting of the oxide at the surface.

Hydrogen electrosorption of single-crystal platinum stepped surfaces and the effects of oxide formation

Hydrogen electrosorption of single-crystal platinum stepped surfaces and the effects of oxide formation