SUS304 Surface Research Articles

Effective removal of uranium (VI) with a SDBS doped PPy-SUS304 electrode from alkaline wastewater using electrodeposition strategy

The immobilization of uranium in nuclear wastewater is of paramount importance for environmental and human health. However, there is a paucity of research on the immobilization of uranium in alkaline wastewater, particularly with regards to the application of novel electrodes. This article presents the utilization of an electrochemically polymerized polypyrrole stainless steel (PPy-SUS304) electrode for the effective electrochemical deposition and removal of uranium from alkaline wastewater containing uranium. According to the electrodeposition results, the uranium deposition efficiency of the novel electrode reached 96.82 %, with a uranium deposition rate of 0.048 mg U/(h·cm2) and a charge efficiency of 0.055 mg U/C. These findings demonstrate the successful electrochemical reduction of UO2(CO3)34- in alkaline uranium-containing wastewater using the novel electrode, resulting in improved charge deposition efficiency. The electrode surface products were investigated using scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and X-Ray Photoelectron Spectroscopy (XPS). The SEM and EDS results demonstrate the formation of a uniform PPy film on the surface of SUS304. In addition, the White light interferometer (WLI) test reveals that the PPy-SUS304 electrode exhibits increased roughness compared to the SUS304 electrode. The XPS results revealed that the electrode surface products of PPy-SUS304 were actually U compounds constituted of U(IV) oxides or hydroxides. This study provides a new perspective for the development of novel electrodes to suppress side reactions and efficiently recover uranium from alkaline uranium-containing wastewater.

The Adhesion Strength of Semi-Clathrate Hydrate to Different Solid Surfaces

The adhesion between a hydrate and a pipe wall is the main cause of hydrate deposition and blockage. In this study, the adhesion strength of semi-clathrate hydrate (tetrabutylammonium bromide hydrate) to four kinds of solid surfaces (E235B carbon steel, E355CC low alloy steel, SUS304 stainless steel, and polytetrafluoroethylene) was measured. This investigation reveals that the adhesion strength of the hydrate to a solid surface is negatively correlated with the wettability of the solid surface, which suggests that hydrophobic materials effectively reduced the hydrate adhesion to the pipe wall. The surface roughness showed different effects on the adhesion of the hydrate to hydrophilic or hydrophobic surfaces. To be specific, when the surface roughness increased from 3.2 µm to 12.5 µm, the hydrate adhesion strength to the hydrophilic surface of SUS304 increased by 123.6%, whereas the hydrate adhesion strength to the hydrophobic surface of polytetrafluoroethylene only increased by 21.5%. This study shows that low wettability and low surface roughness effectively reduce the critical rate required to remove hydrate deposition, which achieves the self-removal of hydrates. At the same time, it was found that the adhesion strength of the hydrate to surfaces increases with increasing subcooling. This investigation holds significant theoretical implications for designing self-cleaning surfaces for oil and gas pipes.

Thermo-selenized stainless steel as an efficient oxygen evolution electrode for water splitting and CO2 electrolysis in real water matrices

Although stainless steel is a promising candidate for oxygen evolution reaction (OER) electrodes, chalcogenization is typically necessary to avoid surface passivation. Herein, we modify the surface of SUS304 by selenization under mild conditions. The optimal selenization temperature (500 °C) is determined by analyzing the surface morphology and elemental distribution. The electrode composition and the role of Se in improving OER activity are clarified using X-ray photoelectron spectroscopy depth profiling. The electrode selenized at 500 °C is rich in oxygen vacancies and had a high Ni content after electrochemical pre-activation. Moreover, the overpotential is only 284.3 mV at 10 mA cm−2 and no potential degradation occurred over 160 h, indicating excellent stability under alkaline conditions. Further, high stability is achieved during CO2 reduction in a real water matrix. These results provide new insights for modifying commercial stainless-steel electrodes to maximize OER activity for alkaline water splitting and neutral CO2 electrolysis.

Effect of Microstructure Evolution and Corrosion Behavior on Phase Transformation of Nanocrystalline SUS304 Prepared by Dry Ice Shot Peening

Microstructure and corrosion behavior of nanocrystalline SUS304 by dry ice shot peening has been investigated in detail in term of phase transformation. SUS304 as metastable austenitic stainless has excellent corrosion resistance and induced martensite by shot peening process. However, the SUS304 has quite low strength which is difficult to wear as metallic component. The dry ice shot peening process was carried out on SUS304 surface for one and three hours. The microstructure was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with electron back-scattered diffraction (EBSD). The phase transformation was analyzed by X-ray diffraction (XRD). The corrosion testing was carried out in 3.5% NaCl solution. The result indicated that the grain size of SUS304 surface was finer by deformation due to dry ice shot peened process. The hardness was improved properly by the increasing the shot peened time, and the corrosion resistance was increased. The XRD results showed that three hours shot peening process induced martensite phase of SUS304 by 15 m thickness. It can be summarized that the dry ice shot peening can be induced phase transformation due to high deformation on the SUS304 surface

Deposition Behavior of Cesium Molybdate on Type 304 Austenite Stainless Steel in Severe Accident

The chemical behavior of cesium molybdate (Cs2MoO4) in light water reactors during severe nuclear accidents remains unexplored. This study demonstrated the deposition behavior of Cs2MoO4 on Type 304 stainless steel (SUS304) at 1530 to 530 K under dry (Ar) and humid (Ar + H2O) conditions. Cesium molybdate was partially decomposed on the SUS304 surface, thereby inducing the oxidation of iron (Fe) and chromium (Cr) under the dry condition. Molybdenum (Mo) metal and molybdenum dioxide (MoO2) were detected on the surface, while Cs coexisted with chromium in the oxide layer at 1500 K. Both Cs2MoO4 and Mo metal were identified on the SUS304 surface at 1230 K. Under the humid condition, the oxidation of the SUS304 was affected by Cs2MoO4 vapor. Molybdenum was detected in the form of spots in the iron oxide layer, while cesium was not detected above 1500 K. Molybdenum metal was detected on the surface of SUS304 oxide at 1230 K. Cesium molybdate was deposited on the SUS304 at 730 to 530 K under both the dry and humid conditions. The results are discussed in relation with the thermodynamic model of the Cs-Fe-Cr-Mo-O system. Thus, the chemical behavior of Cs2MoO4 at the interior of the reactor cooling system is elucidated.

Effect of Crystal Structure on Fabrication of Fine Periodic Surface Structures with Short Pulsed Laser

In recent years, nanostructures have been required for industry and medical services, to perform functions such as reduction in friction, control of wettability, and enhancement in biological affinity. Ultrashort pulsed lasers have been applied to meet these demands, and have been actively studied both experimentally and theoretically in terms of phenomena and principles. In this study, to clarify the phenomenon of the fabrication of laser-induced periodic surface structures (LIPSS), and its application to industry, experiments were conducted on SUS304, titanium, and nickel-phosphorus by a short pulsed laser that has a longer pulse duration, higher cost-effectiveness, and higher stability than ultrashort pulsed lasers. The results confirmed that while LIPSS were fabricated on Ti and Ni-P workpieces, a uniform fine periodic structure was not fabricated on the whole irradiated surface of SUS304, and crystal grain boundaries appeared with low energy density and irradiation number because SUS304 is an alloy composed of Fe, Cr, and Ni. Further, the short pulsed laser has a low power and long pulse duration, inducing the thermal effect. We clarified the effect of crystal structure on fabricating fine periodic surface structures with short pulsed laser.

Effect of Hydrothermal Treatment in Calcium Phosphate Solution on SUS304 Substrate

SUS 304 stainless steel is known to be a biocompatible material and is widely used as screws or plates. However, issues regarding iron ion release after implantation become a concern which limits the application of SUS304. Therefore, to overcome these shortcomings, surface modification on SUS304 by forming calcium layer is needed to disable iron release from the substrate and also to encourage cell attachment. In this study, initially SUS 304 substrate are subjected to electrolysis process in sodium chloride solution to form pitting corrosion. These pitting corrosion will give the anchoring effect for the calcium ions to attach. Then the substrate are subjected to hydrothermal treatment at 200°C in calcium phosphate solution for 24, 36, 48, and 60 hours for deposition of calcium ions on the pitted SUS304 surface. Surface morphology observed by scanning electron microscope (SEM) shows that the calcium ions were deposited on the surface of the SUS304 substrate regardless hydrothermal treatment time. Rockwell hardness values shows that as hydrothermal treatment time increased the hardness value decreases. Therefore, hydrothermal treatment method enables the deposition of calcium ions layer on the surface of SUS304 which will inhibit the release of iron ions and enhanced bone attachment with the implant due to the bonding of the calcium ions with the bone.

High-Temperature Reactions of Cesium Molybdate on 304 Stainless Steel

During a severe accident in a Boiling Water Reactor (BWR), cesium is one of fission products that could be released from nuclear fuel to the reactor vessel and to deposit on the reactor coolant system that is made of stainless steel (SUS). Recently, it has been informed that the released form of cesium is predominantly cesium molybdate. (Cs2MoO4). Under vapor pressure, at high temperature, the deposition of Cs2MoO4 on the surface of oxide SUS could cause some chemical reactions. However, the type of reactions as well as the thermodynamics have not been confimed yet. The aim of this work is to clarify the possible reactions of Cs2MoO4 on the SUS surface at high temperatures. Cs2MoO4 powder was placed in a platinum boat and heated at 1573 K. Either SUS304 or platinum plates were placed downstream at different distances corresponding to temperatures ranging from 1554 to 547 K. The carrier gas was pure argon or argon saturated with steam at 70°C. The flow rate is 100 ml/min. The deposits on SUS304 and platinum plates were examined by X-Ray diffraction equipment (XRD), the micro-Raman spectroscopy and the electron probe micro analyzer (EPMA). The exit gas was passed through the (1%wt HNO3 + H2O) solution. The solution was analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). In dry argon, the obtained deposits on Pt were Cs2MoO4. But on SUS304, the deposits were mainly Mo metal at ~1500 K, then Cs2MoO4 and Cs2Mo2O7 at ~1220K. At further downstream, the deposit were mainly Cs2MoO4. In Ar+steam, on Pt surface, at temperature higher than 1500 K, the deposit could not be obtained, this was probably due to the Cs2MoO4 prefered to stay in gas phase at this stage, but at the temperature below 1200 K, which is close to the melting point (1213 K) of Cs2MoO4, the deposits were predominantly Cs2MoO4. On the surface of SUS304 in Ar+steam, various reactions happened, depending on the temperature. The reaction became even complicated due to the vaporization of CrO2(OH)2. Molybdenum-containing species were found at higher temperatures. But there was no sign of cesium-containing species in SUS304, except for those found on the plates at the low temperatures below ~730 K, where Cs was found as Cs2MoO4.

放射光X線分光を駆使したステンレス鋼表面における自然不動態被膜の構造解析

A native passive film is formed on the SUS304 surface at ordinary temperature and pressure1, 2). As a structural model of the film, a network-structure composed of Cr-oxide and -hydroxide has ever been proposed1, 3), but experimental evidences for the structure have not been reported yet. We examined the detailed film structure using synchrotron X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XAFS spectra clearly showed an ordered network-structure (at least < 10 Å) of Cr(IV) oxide. Additionally, the XPS spectra indicated that the chromium oxide is transformed into a chromium oxyhydroxide such as a -O-Cr-OH- structure. These results are the first evidence that the network structure exists actually in the native passive film of SUS304.

ステンレス鋼 SUS304 のエンドミル切削仕上げ面品位に及ぼす工具摩耗の影響

Machined parts of stainless steels as difficult-to-cut materials are widely used in many industries, which are transportation equipment, electrical machinery, automobile and aerospace industry. This study describes that the characteristics of machined surface by end milling-burnishing method for SUS304 austenitic stainless steel on the vertical machining center. It is found that end milling-burnishing process with using conventional cemented carbide end mill tool can improve finished surface quality of austenitic stainless steel without causing a large change of surface roughness. In this case, the influence of tool wear and surface roughness is discussed. As the result of experiments, width of each cutting edge flank wear land in end milling-burnishing method greatly influences the surface roughness. Finished surface of SUS304 has a surface roughness Rz of 0.18 μm.

Development of thermal spraying materials through several corrosion tests for heat exchanger tube of incinerators

Protective surface treatment via several kinds of cost-effective thermal spraying alternate materials was developed and investigated in this study for heat exchanger tubes in waste incinerators with quite aggressive environment. Different thermal spraying materials including Fusible Ni-SA-a, Fusible Ni-SA-b, Fusible Ni-SA-c, NiCr-TS and NiCr-WEL were investigated to evaluate their performance of corrosion resistance. Three corrosion tests including high-temperature wettability test, long-term adhesion force experiment and hot corrosion test were performed, respectively. As has been proven from experimental results, the specimen coated with Fusible Ni-SA-c exhibited high contact angles in both air and simulated flue gas condition, which indicated a low ash wettability and liquid-bridge force. The coatings of Fusible Ni-SA-c and Fusible Ni-SA-b resulted in quite low adhesion force between ash and specimen, illustrating their good performance to improve the tube corrosion resistance. Besides, the weight losses of specimens coated with Fusible Ni-SA-c and Fusible Ni-SA-b due to corrosion by ash were noticeably decreased, in particular Fusible Ni-SA-c caused almost zero corrosion. Fusible Ni-SA-c decreased the amount of ash deposition on the tube surface of SUS304 by 35%. These corrosion tests supported Fusible Ni-SA-c as thermal spraying material with excellent corrosion resistance, which is able to prevent the heat transfer surface from high-temperature corrosion and thus enhance the service-life of the tube. Furthermore, among these corrosion tests, it was found that the high-temperature wettability test is an effective approach to evaluate the performance of different corrosion-resistant materials.

Preparation of MgO/B2O3 coatings by plasma spraying on SUS304 surface and effects of heat-resistant

This study mainly deals with the preparation of MgO/B2O3 coatings by plasma spraying on the SUS304 surface and the effects of heat-resistant. The power materials of low thermal conductivity were selected to control the heat divergent performance of high temperature parts. The reticular micro-structure between the cover thermal layer and the substrate was prepared by using the plasma spraying method. The powder mixture of MgO and B2O3 were selected as spraying materials and the SUS304 was used as the substrate material. The MgO/B2O3 coating was prepared on the surface of the SUS304 to provide better cover thermal performance. The properties of the microstructures and the morphologies were studied by Optical Microscope, Scanning Electron Microscope, Electron Probe Microanalyzer, and X-ray Diffraction. The results showed that the cover thermal performance has been improved.

無酸素銅とオーステナイト系ステンレス鋼における低変形拡散接合

Achieving good tensile strength and low deformation in the case of diffusion bonding of dissimilar materials is difficult because different materials vary in mechanical properties at high temperatures. In the present study, diffusion bonding of OFC (oxygen-free copper) to austenitic stainless steel SUS304 was carried out under pressures that are suitable for suppressing any deformation of the specimens. The specimens could be bonded above 1073 K, and the bonding time slightly influenced the tensile strength. Convex areas on the bonding surfaces of SUS304 were scarcely deformed, and quite large voids were formed at the bonding interface. The void size decreased with decreasing roughness of the bonding surfaces. However, the specimens polished with emery papers #1000 and #4000 could not be bonded. The tensile strength of the specimens did not change when a nickel film was used as a metallic insert. The fracture occurred at the interface between SUS304 and the nickel film. Bonding could not be realized when the bonding surfaces were not in contact while the temperature increased. Copper and chromium oxide layers exist on the bonding surface of OFC and SUS304, respectively. Bonding was inhibited by the latter layer. The tensile strength was significantly improved when the bonding temperature was raised from 1073 K to 1173 K. Chromium inclusions were observed at the bottom of dimples on the fractured surface, which indicated that the chromium oxide layer cohered at 1173 K. Consequently, the fracture at the base metal of OFC was attained in the specimen obtaining sufficient adhesion between the bonding surfaces. Grain boundaries of the specimen did not migrate across the bonded interface, which suggested that the grain boundary migration was not necessarily required to acquire superior joints.

スパッタエッチングによる薄鋼板および鋼線表面への微細突起物形成

Six kinds of steels with various thickness smaller than 3mm and SUS304 steel wires with 0.5 and 0.2 mm diameter were etched by argon ion sputtering at a radio frequency power of 100-350W for 0.9-19.8ks. Cone-shaped protrusions with various sizes smaller than 5μm were formed on the surface of SK120, SUS304 and SKD61 steel sheets. These protrusions were formed from the bottom of pillar-shaped carbides that precipitate perpendicular to the surface. When the sheet thickness is very small, the conical protrusions were not formed, but the column- or ringshaped protrusions with various sizes smaller than 1μm were formed on the surface of SUS304, SUS316, SUS316L and SKD61 steels. The reason will be that the precipitation of fine pillar-shaped carbides occurs densely due to a small temperature gradient in the thickness direction and the conical protrusions quickly decay to the column- or ring-shaped protrusions. Also for the SUS304 wire, the fine column- or ringshaped protrusions were formed over whole of the surface due to a roundabout of plasma. The sheets and wires with not only the cone-shaped protrusions but also the column- or ring-shaped ones will give wide and flexible applicability to machine parts and structures revealing many functions.

Surface modification of SUS304 stainless steel by atmospheric pressure Ar/N 2/O 2 plasma

The surface characteristics of SUS304 stainless steel are investigated before and after surface modification by Ar/N 2/O 2 plasma under atmospheric pressure conditions. It was found that plasma treatment of a stainless steel plate has a significant effect on the wettability, contact angle, and free energy of the SUS304 surface. The contact angle and surface free energy were analyzed. The optimal surface modification parameters are a power of 1000 W, a torch-to-sample distance of 80 mm, a treatment time of 300 s, and an oxygen content of 1.5 wt%. Under these processing conditions, a contact angle of just 1.60° was obtained. The surface morphology, surface element composition, and surface roughness of the treated SUS304 specimens were examined using scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The results show that the optimal surface modification conditions lead to the formation of fine, uniformly distributed crystallites in the SUS304 microstructure. Moreover, compared to the untreated surface, the treated surface had a significantly lower carbon content and a more uniform distribution of surface peaks.

Interfacial Reactions between Lead-Free Solders and the Multilayer Au/Ni/SUS304 Substrate

Abstract Interfacial reactions between Sn, Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and an Au/Ni/SUS304 stainless steel (SUS304) substrate were conducted using the reaction couple technique at 240, 255 and 270 °C for 1 – 5 h. In the earliest stage of the reaction, only the Ni3Sn4 phase was formed on the Sn/Au/Ni/SUS304 interface. As the reaction time increased to 4 h, the Ni layer was gradually consumed and the Ni3Sn4 phase detached from the interface. Meanwhile, the Sn reacted with the SUS304 to form the FeSn2 phase. In the SAC/Au/Ni/SUS304 reaction couple, both Ni3Sn4 and Cu6Sn5 phases were formed on the interface. When the reaction time exceeded 4 h, the Ni3Sn4 phase disappeared; the Cu6Sn5 phase was spread over the SUS304 surface and the FeSn2 phase was formed on the SUS304 surface. The growth of intermetallic compounds can be described by the parabolic law and the reactions were diffusion-controlled.

C235 ベッセルビームを用いたマイクロドリル加工における材質による加工ダメージの相違(界面)

We investigated a method for reducing work damage in micro-drilling of metals (SUS304, copper, titanium, and aluminum) using a nano-second pulsed Bessel laser beam. Work damage (discoloration and concentric circular marks) due to the side lobs of the Bessel beam are seen on the irradiated surface of SUS304 and copper. On the other hand, in aluminum and titanium, there is little discoloration area on sample surface. In the cases of SUS304 and copper, the absorptivity increases as a result of discoloration due to surface oxidization, and damage is generated. In contrast, for the case of aluminum and titanium, even if the oxide is formed on the surface, neither discoloration nor the changes in absorptivity are remarkable.

1505 ステンレス鋼の超精密切削仕上面に及ぼすマルテンサイト変態の影響(S75-2 高速・高精度加工(2),S75 高速・高精度加工)

This paper deals with the improvement of surface roughness on the ultra-precision cutting of austenitic stainless steels type 304 and 316. Austenitic stainless steels are well known as difficult-to-cut metals. The surface roughness of stainless steel is influenced considerably by the volume of work damaged layer in the field of ultra-precision cutting. The hardness of finished surface depends on the depth of cut and cutting speed. It was found that the work damaged layer is composed of martensitic structures. The deformation-induced martensitic transformation is occurred on the finished surface of austenitic stainless steels. The surface roughness Rz is obtained below 60nm(P-V) under the small effect of the deformation-induced martensitic transformation on the finished surface of SUS304 when the depth of cut is given 2μm.

Chemical States in Oxide Films on Stainless Steel Treated in Supercritical Water: Factor Analysis of X-Ray Photoelectron Spectra

A preliminary study of the corrosion films of stainless steel SUS304 was carried out by X-ray photoemission spectroscopy for supercritical water having no oxidant or reactant. The corrosion films produced by the supercritical water at and were compared with those by anodic polarization in aqueous solution. The chemical states in the films were determined by factor analysis of Fe, Cr, and Ni 2p X-ray photoelectron spectra. Factor analysis of the passivated SUS304 surface was successfully carried out using four reference spectra, Fe metal, , , and FeOOH, with careful treatment excluding wüstite phase from the standpoint of thermochemistry. In the surface treated by supercritical water, the ratio of iron and nickel increased even when compared to the bulk composition of SUS304 and the major component of nickel was attributed to . In contrast, the content of chromium decreased remarkably. This was explained by effective removal of and its protonated form, , which are predicted in the Pourbaix diagram prepared for chromium in supercritical water ( and ).

ホーンを介した水中超音波照射による金属材料表面への圧縮残留応力の付与―液中超音波照射による材料の表面改質（第１報）―

Ultrasonic wave of 19.5 kHz frequency oscillated with an ultrasonic transducer and amplified with a step type of horn was irradiated on metal surface in water to introduce compressive residual stress. Slight plastic deformation occurred at the surface region of pure metal such as Cu and compressive residual stress was introduced. It seemed that the plastically deformed depth from the surface corresponded approximately to the region where the compressive residual stress is extended from the surface. The higher compressive residual stress could be introduced into the surface of Cu-Zn brass and SUS304 stainless steel because work-hardening was simultaneously induced to those alloys. Furthermore, since martensitic transformation was induced by the plastic deformation in the case of SUS304, the lager compressive residual stress could be introduced more deeply into the surface region. The residual stress of SUS304 surface reached to the maximum value of 574 MPa by irradiating for 5 min and the stress extended to the depth of about 170μm from the surface.