Surface Morphology Of Oxide Films Research Articles

Oxide film prepared by selective oxidation of stainless steel and anti-coking behavior during n-hexane thermal cracking

In order to reduce coke formation on the substrate surface, selective oxidation pre-treatments were systematically assessed for 316L stainless steel under H2-H2O atmospheres at 650 °C–950 °C and 0.1 MPa for 10 h. The phase constitution, elemental composition and surface morphology of oxide films were characterized by a combination of SEM, XRD, and EDS. The results showed that the oxidation temperature had a great influence on the morphology and microstructure of oxide films. The Mn and Cr content on the metal surface gradually increased with the increasing exposure temperature. The element composition was mainly associated with MnCr2O4 and Cr2O3. Thickness of oxide films was evaluated in various conditions. The anti-coking performance was evaluated by the n-hexane thermal cracking. It was found that the amount of the coke deposited on the oxidized tube was much smaller than that on the untreated tube, with an average anti-coking ratio of 83.2%. Moreover, the morphologies of carbon deposits were mainly filamentous on the inner surface of untreated tube, but granular for the case of the oxidized tubes.

Influence of the Ti alloy substrate on the anodic oxidation in an environmentally-friendly electrolyte

The influence of the Ti alloy substrate (α, β, α + β) on the anodic oxidation process was studied. The surface morphology, composition and crystalline structure were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). It was shown that the surface morphology and crystalline structure of anodic oxide films were considerably affected by the Ti alloy substrate. The surface morphologies of the oxide films retain their matrix microstructure characteristics. The oxide film on the residual β phase contains a trace amount of V, Zr, Mo element for TA15. Compared to the secondary α phase, the β phase has a higher degree of oxidation for TB6. The oxide film has the higher Al content on the secondary α phase, while the oxide film formed on β-phase has the higher V content. The XPS results show that the Al, Mo, V, Zr alloy elements of TA15 are involved in anodic oxidation and exist as Al2O3, MoO3, V2O5, ZrO2. Likewise, the Al, V alloy elements of TB6 are involved in anodic oxidation and exist as Al2O3, V2O5, but Fe element is not involved in anodic oxidation. The anodic oxide films are partly crystallized and mainly amorphous for the three kinds of titanium alloys. The TA15 anodic oxide film has the highest crystal content, and TB6 has the least.

EFFECT OF Bi ADDITION ON THE CORROSION RESISTANCE OF Zr-lNb ALLOY IN DEIONIZED WATER AT 360 °C AND 18.6 MPa

The effect of Bi contents on the corrosion resistance of Zr-1Nb-xBi (x=0.05—0.3, mass fraction, %) was investigated in deionized water at 360 and 18.6 MPa by autoclave tests. The results show that the corrosion resistance of Zr-1Nb alloy can be improved by adding Bi, and the more the Bi content is, the better the corrosion resistance is. TEM and EDS analyses on the microstructures of the alloys show that there are two types of second phase particles (SPPs), including ZrNbFe and β- Nb. The Bi contents have little effect on the type, size and amount of SPPs, 0.3%Bi can be completely dissolved in α-Zr matrix and has no influence on the solution content of Nb in α-Zr matrix. From the fracture and inner surface morphology of oxide films observed by SEM, it can be seen that the Bi dissolved in the α-Zr could noticeably slow down the microstructural evolution of oxide film, including the propagation of micro-cracks and the transformation from columnar grains to equiaxed grains in the oxide film.

β 相水淬对Zr-4合金在LiOH水溶液中耐腐蚀性能的影响

To investigate the effect ofβ-quenching on the corrosion behavior,Zr-4 specimens wereβ-quenched and subsequently annealed at 480—600℃for 2—200 h.The corrosion tests were carried out in 0.01 mol/L LiOH aqueous solution at 360β/18.6 MPa.The microstructure of Zr-4 specimens and fracture surface morphology of oxide films on the corroded specimens were observed by TEM and HRSEM,respectively.The results show that Zr-4 specimens exhibit excellent corrosion resistance as Zr-Sn-Nb alloys in LiOH aqueous solution after increasing the solid solution content of Fe and Cr inα-Zr matrix by suitable quenching rate fromβ-phase to avoid the formation ofβ-Zr. When the cooling rate is too fast,the specimens show worse corrosion resistance due to the formation ofβ-Zr.After annealing at 480—600℃,the better corrosion resistance of Zr-4 specimens can be obtained with increasing annealing temperture and time due to the decomposition ofβ-Zr.

A superior corrosion behavior of Zircaloy-4 in lithiated water at 360 °C/18.6 MPa by β-quenching

To further understand the mechanism on the heat-treatment effect on corrosion behavior of Zircaloy-4, β-quenched and recrystallized specimens are corroded in an autoclave with 0.01 M LiOH aqueous solution at 360 °C/18.6 MPa. Results show that the β-quenched specimen possesses excellent corrosion resistance, the weight gain of which is consistently comparable to that of ZIRLO and N18 alloys during 529 days exposure, while the recrystallized specimen exhibits accelerated corrosion rate after 100 days exposure. The increase of the supersaturated solid solution contents of Fe and Cr in α-Zr matrix is responsible for the improvement of corrosion resistance by β-quenching treatment. The fracture surface and inner surface morphology of oxide films indicates that β-quenching treatment significantly slow down the development of pores to cracks in oxide films and reduces the uneven growing tendency of the oxide, which is related to the corrosion behavior.

산화막 CMP 공정에서 슬러리 온도 변화에 따른 연마 특성

To investigate the effects of slurry temperature on the chemical mechanical polishing(CMP) performance of oxide film with silica and ceria slurries, we have studied slurry properties as a function of different slurry temperature. Also, the effects of each input parameter of slurry on the oxide CMP characteristics were investigated. The pH showed a slight tendency of decrease, the conductivity in slurries showed an increased tendency, the mean particle size in slurry decreased, and the zeta potential of slurry decreased with temperature. The removal rates significantly increased and maintained at the specific levels over 4<TEX>$0^{\circ}C$</TEX>. The better surface morphology of oxide films could be obtained at 40 <TEX>$^{\circ}C$</TEX> of silica slurry and at 90 <TEX>$^{\circ}C$</TEX> of ceria slurry. It is found that the CMP performance of oxide film could be significantly improved or controlled by change of slurry temperature.