Stainless Steel Films Research Articles

Nanoscale growth twins in sputtered metal films

This article reviews recent studies on the mechanical properties of sputtered copper and 330 stainless-steel films with {111} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering, unusually high strengths, and excellent thermal stability of nanotwinned structures are highlighted.

INFLUENCE OF SUBSTRATE TOPOGRAPHY ON THE NUCLEATION AND GROWTH OF 321 STAINLESS STEEL THIN FILMS PRODUCED BY MAGNETRON SPUTTERING

We have investigated the effects of substrate topography on the nucleation and growth behavior of 321 stainless steel (ss) films, introducing textured surfaces into mica substrates by the abrasion treatment. In this study, two groups of samples were prepared at three different sputtering time within 12 s using radio frequency (r.f.) magnetron sputtering and characterized by atomic force microscopy. Good nucleation uniformity has been obtained on the unabraded mica substrates due to the statistical distribution of nucleation sites. Especially, we have already observed an interesting unusual nucleation phenomenon, the island–rim structure on the abraded mica substrates after 4 s, where the island is fractal-like and the rim around the island was only occupied by few grains for nucleation. These ramified islands were located at the wide grooves introduced as predominate nucleation sites. The island–rim structure formed in initial nucleation process is closely associated with x, y velocity components of surface atoms and the distribution of active sites (related intimately to the surface free energy σ and strain energy ε) for nucleation. With the increasing of the sputtering time, voids and overlarge grains have been observed in the island–rim region after the sputtering time of 8 s and 12 s, respectively.

Amorphous stainless steel coatings prepared by reactive magnetron-sputtering from austenitic stainless steel targets

Stainless steel films were reactively magnetron sputtered in argon/methane gas flow onto oxidized sili- con wafers using austenitic stainless-steel targets. The de- posited films of about 200 nm thickness were characterized by conversion electron Mossbauer spectroscopy, magneto- optical Kerr-effect, X-ray diffraction, scanning electron mi- croscopy, Rutherford backscattering spectrometry, atomic force microscopy, corrosion resistance tests, and Raman spectroscopy. These complementary methods were used for a detailed examination of the carburization effects in the sputtered stainless-steel films. The formation of an amor- phous and soft ferromagnetic phase in a wide range of the processing parameters was found. Further, the influence of the substrate temperature and of post vacuum-annealing were examined to achieve a comprehensive understanding of the carburization process and phase formation.

Thin films with chemically graded functionality based on fluorine polymers and stainless steel

Thin films of stainless steel and poly(tetrafluoroethylene) were co-deposited, by radiofrequency magnetron sputtering, in an inert atmosphere in order to produce a functionally graded material as a coating on a traditional biomaterial, where non-ferromagnetic characteristics and improved wettability must be ensured. These thin films are intended to modify the surface of SS316L used in stents, where the bulk/thin film couple should be regarded as a single material. This requires excellent adhesion of the coating to the substrate. All coatings were deposited with an average thickness of 500 nm. The chemical and phase characterization of the surface revealed that, with the increase in F content, the thin film evolves from a ferritic phase (α) to an amorphous phase with dispersion of a new crystalline ceramic phase (FeF 2). For intermediate F content values, an austenitic (1 1 1) phase (γ) was present. Bearing in mind the envisaged application, the best results were attained for thin films with a fluorine content between 10 and 20 at.%.

INITIAL GROWTH PROCESS OF MAGNETRON SPUTTERING 321 STAINLESS STEEL FILMS OBSERVED BY AFM

To investigate the initial morphological evolution of 321 stainless steel (SS) films, we examined the effect of sputtering time on the morphology of 321 SS film. In this study, a group of samples were prepared at nine different sputtering times within 20 s using radio-frequency (r.f.) magnetron sputtering and characterized by atomic force microscopy (AFM). Only globular-like grains were formed on mica substrates within 6 s, whose average grain size is ~ 21–44 nm. Meanwhile, few grains with larger size are subject to settle at the defect sites of mica substrates. At 8 s, we found large columnar crystallites with the average grain size of 61 nm. From 10 to 14 s, islands grew continuously and coalesced in order to form an interconnected structure containing irregular channels or grooves, with a depth of ~ 3.5–5 nm. Up to 16 s, a nearly continuous film was formed and some new globular-like grains were again present on the film. Study of the AFM image at 20 s suggests that the watercolor masking method designed by us is an effective method, by which we can prepare thin films with steps for the measurement of the thickness of continuous thin films. It is also found that the coverage rate of films increases with the increase in sputtering time (from 2 to 16 s). On the other hand, the increase in root mean square (RMS) roughness is much more significant from 6 to 10 s, and there is a maximum value, 2.81 nm at 10 s due to more islands during deposition. However, RMS roughness decreases with the decrease in length and width of channels or grooves from 10 to 16 s. Especially, a lower RMS roughness of 0.73 nm occurs at 16 s, because of the continuous film produced with a large coverage rate of 98.43%.

An optical and electrical layered sensor for the measurement of ingredients in liquid

In this paper, an electrical and optical layered sensor is proposed as a new, non-invasive sensing method for the measurement of ingredients in liquid, particularly in the food industry. In the proposed sensor, the optical properties of the liquid are measured by a light-emitting diode (LED) and a photodiode, and the electrical properties are measured by indium tin oxide (ITO) film electrodes with the transparent conductive properties arranged on the surfaces of the LED and the photodiode. Thus, the electrical and optical properties in the same space of the liquid can be simultaneously measured at a single sensor. To test the sensor experimentally, two parameters of a liquid—such as concentrations of red color and sodium chloride (NaCl) between 0.1% and 0.5% in distilled water—were estimated using measurement values of the electrical and optical properties obtained with the proposed sensor. In addition, it was found that two other parameters of a liquid, such as coffee and milk concentrations between 0.1% and 1.0% in distilled water, could also be estimated with the proposed sensor. The measurement values of optical properties with and without the ITO film and those of electrical properties using an ITO film electrode and a stainless-steel film electrode were also compared. The results suggested that it is possible to measure both optical and electrical properties using the proposed sensor, although there are still some problems such as the surface resistance and transmittance of the ITO film that must be addressed.

Deposition and properties of high-carbon iron films

Thin high-carbon iron films were deposited by pulsed laser deposition onto grids for transmission electron microscopy using pre-combined carbon/iron targets with equal area ratio. The deposited films of about 20 nm in thickness were directly characterized by transmission electron microscopy. The films showed a variety of phases, surprisingly also including the NaCl-type FeC phase, which was theoretically predicted in the literature. For comparison, thin high-carbon stainless-steel films were deposited onto oxidized Si wafers with different carbon ratios in the targets (10, 20, 40 and 50 at.%). These films were characterized by means of Mössbauer Spectroscopy, the magneto-optical Kerr-effect, grazing incidence X-ray diffraction and Rutherford backscattering spectrometry. With these methods clearly defined multilayer-structures were observed which could lead to interesting magneto-resistance phenomena if the thickness of the multilayers can be controlled by the processing parameters.

Nitriding of Fe–Cr–Ni films by low energy ion implantation

Nitrogen low energy implantation was carried out simultaneously into thin austenitic stainless steel films, deposited by ion-beam sputtering, and bulk samples with the aim to investigate the influence of the grain size and microstructure on diffusion and phase formation. Nitrogen uptake, diffusion and phase formation were investigated using SIMS, XRD and TEM. The diffusion itself is very similar in bulk material and thin films, indicating that the grain size differing by close to a factor of 1000 is not the dominating factor. In contrast, the transition towards CrN precipitates within a martensitic host was only found for the thin films implanted at 360 °C.

Influence of ultrasonic cavitation on passive film of stainless steel

The electrochemical behaviors of passive film of stainless steel 0Cr13Ni5Mo under the condition of static state (quiescence) and ultrasonic cavitation in the HCl solution have been studied by means of polarization curve, electrochemical impedance spectroscopy (EIS) and capacitance potential measurement. The results indicate that the passive film shows a multi layer structure distribution, and presents a p-type semiconductor property under the condition of quiescence. The stability of passive film decreases, the semiconducting property changes to an n-type semiconductor in the presence of cavitation. The amount of transition electrons from valence band because of cavitation is related to the height of Fermi level of passive film semiconductor.

Influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel films

The authors have studied the influence of deposition rate on the formation of growth twins in sputter-deposited 330 austenitic stainless steel thin films. Transmission electron microscopy shows that the volume fraction of twinned grains increases with increasing deposition rate, whereas the average columnar grain size and twin spacing stay approximately unchanged. These experimental results agree qualitatively with their analytical model that predicts deposition rate dependent formation of growth twins. The film hardness increases monotonically with increasing volume fraction of twinned grains.

Electrochemical Behavior of Oxide Films of Stainless Steel in 40 kHz Sonicated Sulphate Electrolytes

This paper describes effects of 40 kHz ultrasound on the oxide films of stainless steel in sulphate electrolytes so as to determine the transmitted power and to characterize mass transfer and peak current density on the electrode surface. Emphasis was mainly laid on electrochemical oxidations and peeling mechanism of oxide films in sonicated sulphate solutions (0.5 and 1.0 mol/L). Polarization voltammetry, current response traces and SEM analysis were carried out in order to provide full information as to oxide films surface. Results shows that the rate of electrochemical oxidation, the shape of polarization curves and the surface micrographs in sonicated sulphate electrolytes are different from those obtained without introduction of ultrasound. It is concluded that ultrasound can change the electro-chemical behavior of oxide films by its cavitaion effects, which would produce transient mechanical impulsive force and enhance electrochemical reactions.

The Gibbs–Thomson effect in magnetron-sputtered austenitic stainless steel films

Magnetron sputtering of austenitic stainless steel AISI 316, which has a face-centred cubic structure(γ), leads to films exhibiting a body-centred cubic(α) structureor a mixture of α- and γ-phases. The microstructure of the deposited films was studied by Mössbauerspectroscopy, x-ray diffraction and transmission electron microscopy.With increasing deposition temperature a phase transformation fromα- toγ-phase was observed in these films. Instantaneous recording of the electromotive forceshows that nickel content and deposition temperature are crucial factors for phase stabilityand phase formation. In room temperature deposited stainless steel films, the phasetransformation after vacuum annealing can be described by the Johnson–Mehl–Avramikinetic model. These phase transformations in stainless steel films during annealing can beexplained with the Gibbs–Thomson effect, where the grain boundary energy raises theGibbs free energy.

Fluorescence lifetime imaging study of a thin protein layer on solid surfaces

Understanding the fundamental interactions between proteins and solid surfaces is essential in the area of implantable medical devices. Fluorescence methods offer the sensitivity required to study the formation of the initial thin protein layers that mediate biocompatibility of materials. Thin protein layers (bovine serum albumin labelled with 1-anilino-8-naphthalenesulfonate, BSA–ANS) deposited on several surfaces (glass, silicon, stainless steel, polystyrene, and silver island film) were studied using confocal frequency domain Fluorescence Lifetime Imaging Microscopy (FLIM) and single-point multifrequency lifetime analysis techniques. FLIM provides spatial information about both fluorophores located on the surface and physicochemical parameters of the surface microenvironment. The average fluorescence lifetimes ( τ av) of the adsorbed BSA–ANS generated by the contact between a protein solution and the material surface were measured by the multifrequency modulation and phase shift. Results indicate that τ av values of the albumin complexes on the surfaces (∼ 12 ns) are, in general, shorter than τ av found in the bulk solution (∼ 14 ns). For some surfaces, like polystyrene and silver island film the differences in τ av of the adsorbed BSA–ANS were found to be much greater. The differences in fluorescence lifetimes may indicate structural changes in the BSA protein induced by contact with the surface.

2741 ステンレス冷延鋼板の表面性状と油膜厚さの関係(S24-2 塑性加工(2),S24 塑性加工の動向とその展開)

2741 ステンレス冷延鋼板の表面性状と油膜厚さの関係(S24-2 塑性加工(2),S24 塑性加工の動向とその展開)

表面から放出される気体の分析―昇温脱離法―

Thermal desorption spectroscopy (TDS) has been commonly employed to evaluate the outgassing properties of both vacuum materials and thin films. Hydrogen, water, CO and CO2 —the most dominant gas species— can be easily detected and quantified by quadrupole mass spectrometry. This paper examines two calibration methods to convert ion current into outgassing rate: first, by using the standard leak of each gas and, second, by using an absolute pressure gauge. TDS is demonstrated for two different types of samples: stainless steel and amorphous Si (a-Si) film. In the case of stainless steel, samples blasted with glass beads were compared with chemically polished samples, and the TDS results' relationship to pumping down properties was investigated. The a-Si film examined was formed using a low temperature poly silicon process. Its hydrogen concentration as determined by TDS corresponded with that obtained by secondary ion mass spectrometry (SIMS). The outgassing temperature characteristics obtained for both the stainless steel and a-Si samples provided valuable information.

스테인리스 강 박막 및 기판을 이용한 배열형 정전용량 압력센서의 전기 기계적 특성연구

In this work, mechanical characteristics of stainless steel diaphragm have been studied as a potential robust substrate and a diaphragm material for micromachined devices. Lamination process techniques combined with traditional micromachining processes have been adopted as suitable fabrication technologies. To illustrate these principles, capacitive pressure sensors based on a stainless steel diaphragm have been designed, fabricated and characterized. The fabrication process for stainless steel micromachined devices keeps the membrane and substrate being at the environment of 8.65㎫ pressure and 175℃ for a half hour and then subsequently cooled to 25℃. Each sensor uses a stainless steel substrate, a laminated stainless steel film as a suspended movable plate and a fixed, surface micromachined back electrode of electroplated nickel. The finite element method is adopted to investigate residual stresses formed in the process. Besides, out-ofplane deflections are calculated under pressures on the diaphragm. The sensitivity of the device fabricated using these technologies is 9.03 ppm ㎪?¹ with a net capacitance change of 0.14 ㎊ over a range 0~180 ㎪.

Nanostructured coated powders for structural net shape components

The specific goal of the present study is to evaluate the surface performance of thin films based on sputtered stainless steel (304 AISI) deposited on dissimilar (Cu) and similar powder materials (316 AISI) with different size distributions and shapes. The covering efficiency, the surface morphology and the grain size, and their impact on the flowability of powders, are studied. The most important role of powder surface treatments is attained when spherical powders of copper were coated with a nanocrystalline thin film of stainless steel, the flowability increases by 80%. However, in the stainless steel powders the presence of a similar coating has relevance only for irregular particles, where a 25% flowability improvement is measured.

Scanning CO2laser bacterial inactivation systems

The performance of three scanning CO(2) laser inactivation systems was assessed and included: a gantry system, a rapidly rotating mirror and a low-power hybrid system combining an oscillating mirror and rotary motion of the sample. Escherichia coli and Staphylococcus aureus were the target organisms on stainless steel, nutrient agar or moist collagen film and the laser power was varied from 2 to 1060 W (two laser sources). In general, a threshold energy density was identified, above which no inactivation was observed because the scanning velocity was too high (10 cm s(-1) for stainless steel, 660 W). Reducing the velocity increased the inactivation process until complete inactivation was observed at 1.3 cm s(-1) (E. coli, approximately 10(6) CFU per sample) and 0.82 cm s(-1) (S. aureus, approximately 10(8) CFU per sample); consequently, S. aureus organisms showed a greater resistance to laser irradiation. For the nutrient agar and collagen samples, the averages of the width of clearing were measured as a function of the translation velocity and the rates of inactivation (I(R), cm(2) s(-1)) were found; an optimum velocity was observed that produced the maximum rate of inactivation. At a laser power of 1060 W, the maximum value of I(R) was 140 cm(2) s(-1) ( approximately 10(7) CFU cm(-2)) for S. aureus on collagen and slightly less on nutrient agar (114 cm(2) s(-1), estimated from a best-fit polynomial, r(2) = 0.98). A comparison of the low- and high-power lasers produced values of 0.09 cm(2) s(-1) W(-1) (i.e. I(R) per Watt delivered) for S. aureus on nutrient agar with the low-power laser at 13 W and on collagen 0.13 cm(2) s(-1) W(-1) for 1060 W. The rate of inactivation was found to be a function of the laser power, translation velocity and properties of the substrate media. The three laser inactivation systems successfully demonstrated the potential speed, efficiency and application of such systems. Laser scanning systems offer the potential for rapid and efficient inactivation of surfaces, eliminating the need for chemical treatment.

Bactericidal and corrosive properties of silver implanted TiN thin films coated on AISI317 stainless steel

The bactericidal and corrosive property of Ag +-implanted AISI317 stainless steel and TiN thin films coated on AISI317 substrate were investigated using Gram positive bacteria Staphylococcus aureus ( S. aureus) and electrochemical measurements. The silver ion implantation was performed with the dose ranging from 5 × 10 16 to 5 × 10 18 ions/cm 2 at an energy of 70 keV. The samples were characterized by X-ray Photoelectron Spectroscopy (XPS). The results indicate that the high dose Ag +-implanted samples show the antibacterial activity obviously but high dose implantation reduced the corrosion resistance correspondingly. There is an optimum ion dose of 1 × 10 18 ions/cm 2 at which both bactericidal and anticorrosion properties are kept complement. Based on some results on surface characterization, the mechanism of the antibacterial properties and corrosion resistance are discussed.

Destruction of Deinococcus geothermalis biofilm by photocatalytic ALD and sol-gel TiO2 surfaces

The aim of the present work was to explore possibilities of photocatalytic TiO2 coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms on stainless steel, glass and TiO2 film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45 degrees C under vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1-0.3 microm in length. Adjacent cells were connected to one another by threads of 0.5-1 microm in length. An ultrastructural analysis gave no indication for the involvement of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO2 surfaces, submerged in water, were exposed to 20 W h m(-2) of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >10(7) down to below 10(6) cells cm(-2)). TiO2 films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of the TiO2 with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO2 surfaces have potential as a self-cleaning technology for warm water using industries.