Hydrogenated amorphous carbon films deposited on 316L stainless steel

Research on hydrogen amorphous carbon films (a-C:H), which possess the diamond-like characteristic, has been stimulated for many years by need to simultaneously optimizing the mechanical, optical and biological properties, and by challenges related to the deposition of a-C:H films on medical implants. In the present work, we investigate the structure, optical and mechanical properties (hardness, elastic modulus and stress) of a-C:H films deposited on 316L stainless steel substrate by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD). The negative self-bias voltages significantly influence on temperature of steel substrates during the deposition process and films properties. Specifically, the high energetic deposition leads also to stabilization of the sp² content and thermally-activated relaxation in the stress of a-C:H films. Presented correlation between the obtained results and literature analysis let deem the Raman spectra as a good tool to control the properties of implants made of 316L stainless steel with a-C:H film for general use.     

316L不锈钢表面脉冲电镀钯的性能

以316L不锈钢为基体,分别采用脉冲电镀和直流电镀法制备了钯膜层。对比研究了脉冲电镀钯和直流电镀钯的微观结构、显微硬度、孔隙率、耐蚀性等性能。与直流电镀钯膜层相比,脉冲电镀钯膜层更为均匀、致密,晶粒尺寸更小,孔隙率更低,显微硬度更高,附着力更强。另外,脉冲电镀钯膜层在80°C的20%H2SO4和20%H2SO4+0.001 mol/L Cl-中的耐腐蚀性均优于直流电镀钯膜层。     

Tribological properties of DLC films deposited on steel substrate with various surface roughness

Tribological properties of diamond-like carbon (DLC) films in water were investigated concerning with the influence of surface roughness and various mating materials. The DLC films were deposited by pulsed-bias CVD method on AISI630 stainless steel. The substrate roughness (R_a) is in the range of 1.4–740 nm. AISI 440C, AISI 304 stainless steel and brass balls were used as a mating ball. The friction coefficients of DLC films against with AISI 440C stainless steel ball indicated under 0.1 irrespective of the roughness. The film having smooth surface (R_a=1.4 nm) had severe damage at a load of 9.4 N. However, the film having rough surface (R_a=263 nm) had no damage at the same load. The specific wear rate of the steel ball increased with increase of roughness of the surface. In the case of AISI 304 stainless steel ball, the specific wear rate of the ball showed similar tendency. The friction with brass ball showed relatively high friction coefficient in the range of 0.12–0.25. However, the damage on the films could not be observed after friction test. It is considered that the roughness of the surface is important factor for the rupture of the film in water environment.     

Blood compatibilities of carbon nitride film deposited on biomedical NiTi alloy

Carbon nitride (CNx) film, diamond-like carbon (DLC) film, and titanium nitride (TiN) film were deposited on biomedical NiTi alloy substrates using direct current magnetron sputtering, respectively. In order to improve the adhesive strength between the deposited hard film and the NiTi alloy, a Ti transition layer was pre-deposited firstly. We emphatically evaluated the blood compatibilities of the NiTi alloy substrate and the deposited hard films by haemolysis test and platelet conglutination test. It was shown that the blood compatibilities of NiTi alloy can be improved effectively by the deposition of hard films. In comparison with TiN and DLC film, CNx film had the best surface modification effects covering the minimum haemolysis ratio and the best anticoagulation property.     

Corrosion resistance and photocatalytic activity evaluation of electrophoretically deposited TiO2-rGO nanocomposite on 316L stainless steel substrate

TiO₂-rGO nanocomposite coatings were obtained by electrophoretic deposition (EPD) technique of TiO₂ nanoparticles and graphene oxide (GO) on stainless steel substrate. First, GO particles were synthesized using a modified Hummers' method. GO was reduced electrochemically to form a coating in the presence of nano-sized TiO₂ particles. The influences of different parameters such as GO concentration, coupling co-electro-deposition parameters (electrophoretic duration and voltage) on thickness, surface morphology and, corrosion behavior of the as-synthesized TiO₂-rGO nanocomposite coatings were systematically surveyed. The morphology and microstructure were investigated by field emission scanning electron microscopy (FE-SEM), Raman spectra and X-ray diffraction (XRD) techniques. Atomic force microscopy (AFM) was harnessed to evaluate the topography of the as-prepared GO powder. The bonding characteristics of as-synthesized and as-reduced GO were examined after deposition, by Energy Dispersive Analysis of X-Ray (EDX) and Fourier-transform infrared spectroscopy (FT-IR). Corrosion behavior of coatings and that of the pure TiO₂ layer were evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques (by applying potentiodynamic polarization spectroscopy (PDS)). Detailed SEM studies showed that increasing EPD voltage brings about a coating with increased porosity and microcracks with higher thickness. In addition to that, the presence of rGO reduced corrosion current density (i_corr) and shifted corrosion potential (E_corr) toward more noble values in 3.5% NaCl at room temperature. Also, Analyses revealed that the optimum electrophoretically synthesized coating was obtained at GO concentration of 1 g/L, 30 V and 30 min at room temperature. The corrosion current density of the corresponding coating was remediated up to 0.2 μA cm⁻², which means an anti-corrosion ability of about 30 times compared to TiO₂-coated and bare 316L stainless steel. The results of impedance spectroscopic studies demonstrated that this coating renders as a barrier layer and resistance increased from 2.95 KΩ cm² for TiO₂-coated layer to 10.49 KΩ cm² for the optimized layer.     

Reactive sputter-deposition of oxygenated amorphous carbon thin films in Ar/O2

Oxygenated amorphous carbon thin films were deposited by DC magnetron sputtering using various argon and oxygen process gas mixtures. The X-ray diffraction data indicated that the predominantly amorphous films had more defined peaks with a higher partial pressure of oxygen. Results indicated that use of oxygen in the working gas enhanced the crystalline nature of the films. Scanning electron and atomic force microscopy revealed that the surface roughness and film topography differed with the oxygen process gas variations. X-ray photoelectron spectroscopy revealed increased surface oxygen content with higher oxygen concentration in the working gas. Raman spectroscopy results suggested that the increased oxygen in the films may have led to a higher percentage of sp³-bonded carbon atoms. The growth rate (deposition rate) of the films decreased as the amount of oxygen increased. This decreased deposition rate was associated with an oxygen etching of the film.     

Argon plasma treatment techniques on steel and effects on diamond-like carbon structure and delamination

We demonstrate alteration in diamond-like carbon (DLC) film structure, chemistry and adhesion on steel, related to variation in the argon plasma pretreatment stage of plasma enhanced chemical vapour deposition. We relate these changes to the alteration in substrate structure, crystallinity and chemistry due to application of an argon plasma process with negative self bias up to 600 V.Adhesion of the DLC film to the substrate was assessed by examination of the spallated fraction of the film following controlled deformation. Films with no pretreatment step immediately delaminated. At 300 V pretreatment, the spallated fraction is 8.2%, reducing to 1.2% at 450 V and 0.02% at 600 V. For bias voltages below 450 V the adhesion enhancement is explained by a reduction in carbon contamination on the substrate surface, from 59 at.% with no treatment to 26 at.% at 450 V, concurrently with a decrease in the surface roughness, R_q, from 31.5 nm to 18.9 nm. With a pretreatment bias voltage of 600 V a nanocrystalline, nanostructured surface is formed, related to removal of chromium and relaxation of stress; X-ray diffraction indicates this phase is incipient at 450 V. In addition to improving film adhesion, the nanotexturing of the substrate prior to film deposition results in a DLC film that shows an increase in sp³/sp² ratio from 1.2 to 1.5, a reduction in surface roughness from 31 nm to 21 nm, and DLC nodular asperities with reduced diameter and increased uniformity of size and arrangement. These findings are consistent with the substrate alterations due to the plasma pretreatment resulting in limitation of surface diffusion in the growth process. This suggests that in addition to deposition phase processes, the parameters of the pretreatment process need to be considered when designing diamond-like carbon coatings.     

Investigation of oxide film formation on 316L stainless steel in high-temperature aqueous environments

Oxide films were grown on the surface of 316L stainless steel subjected to high temperatures and a high-pressure aqueous environment (250 °C and 7 MPa). The morphology, chemical compositions and corrosion properties of oxide films were investigated by scanning electron microscopy (SEM), auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The results indicated that oxide films formed at 250 °C were more corrosion resistant and thicker than were oxide films formed in air at room temperature (25 °C). These distinctions are correlated with the structure and chemical compositions of oxide films. It was found that both films contained a double-layer structure comprised of mixed iron–nickel oxides and chromium oxides. Iron was present as FeO, Fe₂O₃ and FeOOH; Cr was present as Cr₂O₃, Cr(OH)₃ and CrO₃; and Ni existed as Ni(OH)₂ within the oxide films formed at 250 °C.     

Growth of platinum nanoparticles on stainless steel 316L current collectors to improve carbon-based supercapacitor performance

In this study, an improvement in the supercapacitive behavior of a symmetrical carbon-based supercapacitor is achieved by modifying the stainless steel current collector using platinum nanoparticles (PtNs). The PtNs are allowed to grow on the surface of the current collectors before they make contact with the surface of activated carbon electrode monoliths prepared from pre-carbonized rubber wood sawdust. All of the methods used in the present study, i.e., electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge tests provide consistent results, suggesting that the monolithic form of carbon electrodes and PtNs play a significant role in reducing the equivalent series resistance from 337 to 18 mΩ and to increase the specific capacitance from 108 to 151 F g⁻¹. This change improves the specific energy from 2.5 to 3.3 Wh kg⁻¹ and the specific power from 275 to 288 W kg⁻¹, respectively.     

A sol-gel based bioactive glass coating on laser textured 316L stainless steel substrate for enhanced biocompatability and anti-corrosion properties

In this study, we have synthesized a new family of bioactive glass (BAG) comprising of SiO₂, Na₂O, CaO, K₂O, P₂O₅ and MgO via sol-gel route. The composition of these oxides has been selected in such a way that the BAG has a coefficient of thermal expansion close to the 316L stainless steel (SS). In vitro test by soaking the BAG in simulated body fluid (SBF) showed good bioactivity due to ion exchange between alkali ions from the BAG and the ions present in the SBF. The 316L SS substrates were textured using laser before application of BAG using sol-gel dip coating. Pull off test showed that the adhesion strength in case of textured and non-textured surfaces were 4.2 MPa and 2.46 MPa, respectively. This implies that texturing of the surface is helpful in increasing the adhesion strength of the coating. The bioactive glass-coated textured surface of 316L SS substrate showed better corrosion resistance in SBF than the bare substrate for which the respective corrosion current densities were 35 nA/cm² and 353 nA/cm², thereby indicating that the single layer sol-gel dip coating of bioactive glass improved the corrosion resistance of the 316L SS implants. The analysis of scanning electron microscopy (SEM) images of the coating after immersion in SBF shows the formation and growth of the apatite layer that will further inhibit the corrosion of the substrate. These results demonstrate the potential of the synthesized BAG as a coating material for 316L SS implants.     

Enzyme-induced ennoblement of AISI 316L stainless steel: Focus on pitting corrosion behavior

The use of purified enzymes in microbial influenced corrosion (MIC) studies is increasingly recognized as a powerful tool to understand electrochemical interfacial processes, especially the ennoblement of stainless steels (SS) in natural waters. The ennoblement has attracted the interest of many researchers as the consequences in terms of pitting corrosion are still not well understood.In the present study, the ennoblement of AISI 316L SS was induced by glucose oxidase (Gox) catalyzed reaction or by adding hydrogen peroxide (H₂O₂) in synthetic fresh water, on the basis of previous work. The corrosion behavior of the sample was studied using potentiodynamic and galvanostatic polarization tests. When the ennoblement occurs, the pitting potential (E_p) becomes nobler as well. The involvement of H₂O₂ to enhance pits repassivation seems to be a key consideration in this respect.Results obtained using this enzymatic system enable us to reappraise the commonly acknowledged hypothesis that the ennoblement increases the risk of localized attacks.     

类金刚石薄膜在人工关节摩擦副表面改性进展

类金刚石（DLC）薄膜由于其优异的减摩耐磨性以及良好的生物相容性被引入到人工关节材质中。该文综述了DLC薄膜在人工关节摩擦副表面改性的研究现状,包括DLC薄膜的分类和制备方法。尽管该薄膜已被研究数十年,但在人体复杂的生理力学环境中高负荷摩擦腐蚀等综合作用下,仍存在高内应力导致结合力不足,从而限制其在人工关节领域的应用。该文介绍了降低DLC薄膜内应力提高膜基结合力的方法和DLC薄膜生物相容性的研究进展。最后,对不同DLC薄膜人工关节摩擦副的研究进展进行了阐述。根据该综述,提出厚的无氢DLC涂层（高sp3含量）,且在两个滑动表面上均有DLC薄膜的人工关节副具有优异的耐磨性,对于承重植入体应用至关重要。     

Single pit initiation on 316L austenitic stainless steel using scanning electrochemical microscopy

Scanning electrochemical microscopy was used to locally release a controlled amount of chloride ions close to a 316L austenitic stainless steel (SS) substrate in sulphuric acid medium to generate a single pit. Then, usual electrochemical techniques were applied for studying the early stages of pit initiation and propagation. The amount of chloride ions needed to reach the requisite threshold concentration for pit initiation was determined. It was found to be higher for SS than for pure iron. The amount of dissolved cations was also determined as a function of the substrate potential. Different pit shapes and depths were observed depending on the potential applied to the substrate. Following the pit repassivation, it was observed that a part of the dissolved products precipitated at the bottom of the pit.     

Hydrogen effects on pitting corrosion and semiconducting properties of nitrogen-containing type 316L stainless steel

The effects of hydrogen pre-charging on pitting corrosion resistance and semiconducting nature of passive film formed on two different nitrogen-containing type 316L stainless steel (0.076 and 0.086 wt% N) have been studied. Auger electron spectroscopy (AES) analysis of the alloys after passivation indicated weak nitrogen peak, but the presence of nitrogen and NH₃/NH₄⁺ was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis. The results of pitting corrosion in 0.5 M NaCl (pH ≈ 5.7) solution revealed that hydrogen increased the passive current density and significantly reduced the pitting resistance. In 0.3 M H₃BO₃ + 0.075 M Na₂B₄O₇·10H₂O (pH ≈ 8.45) solution, increase in passive current density without affecting the breakdown or transpassive potential was observed for both the alloys. Electrochemical impedance spectroscopy (EIS) measurement after hydrogen pre-charging showed decrease in semi-circle radius of Nyquist plot, and the polarization resistance, R_P associated with the resistance of the passive film. The decrease was significant with increasing hydrogen-charging current density (−50 to −100 mA/cm²). The results of the capacitance measurement and Mott–Schottky plots revealed that passive films exhibit n-type and p-type semiconductivity films for both the uncharged and hydrogen charged specimens of the investigated alloys. Doping densities obtained from Mott–Schottky plots increased with hydrogen pre-charging. The overall results indicated that hydrogen pre-charging deteriorated the passive film stability and lowered pitting corrosion resistance. The effects of hydrogen pre-charging on pitting corrosion, passive film and semiconducting properties are discussed in light of the above results.     

A new precursor for fabricating TiN coating on 316L stainless steel at low temperature without corrosive byproducts

High quality TiN coated 316L stainless steel can hardly be fabricated by the traditional chemical vapor deposition (CVD) methods because of the formation of HCl (g) corrosive byproduct and phase transformation at high deposition temperature. To address the problem, herein, for the first time a novel TiCl₂ precursor is proposed to fabricate TiN coating on 316L substrate in N₂ atmosphere at low temperature. The idea is based on that metastable TiCl₂ can release fresh Ti atoms by its disproportionation reaction, and then the fresh Ti atoms react easily with N₂ to form TiN coating at low temperature without HCl byproduct. The reaction path, interface reaction, and performance of the TiN coating were investigated. The optimized nanograin TiN (45 nm) coating was successfully fabricated on 316L at 750 °C and it exhibited excellent corrosion resistance.     

A systematic study on the changes in properties of an activated carbon cloth upon polarization

The effects of polarization on properties of activated carbon cloth (ACC) have been investigated systematically. The polarization-treated ACC samples were prepared by polarizing them in Na₂SO₄ or KH₂PO₄/KOH buffer solutions at potentials from −1.5 to 5.0 V. The properties, such as surface area, pore size distribution (PSD), total pore volume, amount and nature of the surface functional groups and surface acidity, of pristine and polarization-treated ACC samples were determined. The samples were also characterized electrochemically by determining the properties such as specific capacitance and potential at point of zero charge (E_PZC). Anodic polarization in different electrolytes was found to cause oxidation on ACC. Although the surface textural properties did not change considerably, the changes took place in chemical and electrochemical properties upon anodic polarization were found to be important. The increase in surface acidity shifted the pH_PZC from 7.40 to 3.21 and E_PZC from 164 to 355 mV. The optimum potential range, considered to be safe for polarization of ACC, was determined as −1.5 to +0.8 V.     

The tribocorrosion behaviour of YSZ coating deposited on stainless steel substrate in 3.5 wt% NaCl solution

The YSZ coating was applied to 304 stainless steel substrate by atmospheric plasma spraying technology, and its electrochemical and tribological properties in 3.5 wt% NaCl solution were studied. In electrochemistry, under the action of cathode and anode potential, observe the changes of corrosion current density and EIS before and after wear. The results show that the YSZ coating has a very low corrosion current density during wear and corrosion compared to 304 stainless steel, and after the condition of the anode potential is applied, the effect of friction on the electrochemical impedance of the YSZ coating is very low, while the 304 stainless steel Impedance performance decreases; In terms of tribology, the friction coefficient of 304 stainless steel in 3.5 wt% NaCl solution is easily affected by potential, and the friction coefficient of YSZ coating relative to 304 stainless steel only changes under high potential. As the potential increases, the material volume loss of 304 stainless steel and YSZ coating increases linearly. From the data, the volume loss caused by the corrosion and wear of 304 stainless steel is much higher than that of YSZ coating.     

炭黑硬度对胶料与钢丝帘线粘合力的影响

研究炭黑N326粒子硬度对轮胎带束层胶料物理性能以及胶料与钢丝帘线粘合力的影响.结果表明,随着炭黑N326粒子硬度的增大,带束层胶料门尼粘度、MH、ML、邵尔A型硬度、定伸应力和拉伸强度增大,拉断伸长率减小,焦烧时间和正硫化时间缩短;炭黑N326粒子硬度对硫化胶与钢丝帘线粘合力影响较大,两者呈正比关系.     

316L钢在含H_2S、Cl~-水溶液中的慢应变速率腐蚀试验研究

通过慢应变速率法 (SSRT)应力腐蚀试验 ,得到了 31 6L钢的应力腐蚀敏感性指数 ,回归出计算应力腐蚀敏感性指数的方程 ,表明水溶液中Cl- 对 31 6L钢的应力腐蚀影响较大 ,而H2 S的影响小。