含铜铁素体抗菌不锈钢的杀菌机理的初步研究

通过杀菌性能、蛋白质溶出、添加半胱氨酸等实验，并利用生物透射电镜技术，对含铜铁素体抗菌不锈钢对大肠杆菌的杀灭作用机理进行了初步研究。结果表明抗菌不锈钢对大肠杆菌的杀菌率达到99．99％。进一步的研究发现，大肠杆菌与抗菌不锈钢作用后，其细胞壁和细胞膜破裂，细胞膜脂质和含-SH等还原基团酶发生氧化，细胞内出现了明显的内含物溢出现象。随着与抗菌不锈钢作用时间的延长，细菌细胞内的蛋白质漏出量不断增加，最终致使细菌死亡。     

Study on antibacterial mechanism of copper-bearing austenitic antibacterial stainless steel by atomic force microscopy

A study was made on the antibacterial mechanism of copper-bearing austenitic antibacterial stainless steel by a series of methods such as atomic force microscopy (AFM) observation, force-distance curves and inductively coupled plasma mass spectrometer test. It was observed by AFM that the structure of the outer cell membrane responsible for the cell permeability was substantially changed for the bacteria after contacting with the antibacterial stainless steel, showing that cell walls were seriously damaged and a lot of contents in the cells leaked. It was also found that the adhesion force of bacteria to antibacterial stainless steel was considerably greater than that to the contrast steel, indicating that the electrostatic forces by Cu(2+ )being an important factor for killing bacteria.     

含铜奥氏体抗菌不锈钢抗菌性能和机理初步研究

考察了含铜奥氏体抗菌不锈钢的抗菌性能，并对其抗菌机理进行了初步探讨。方法：覆膜法测定杀菌率；透射电镜观察E．coli细胞形态；考马斯亮蓝法测定细胞漏出液中可溶性蛋白含量；琼脂糖凝胶电泳检测菌体基因组DNA考察抗菌不锈钢对DNA的剪切作用。结果：除产气肠杆菌外，奥氏体抗菌不锈钢对其它供试的16种常见微生物均显示较强的抗菌活性，具有广谱抗菌性．在作用9h时可将1×10^7cfu／ml的E．coli全部杀灭，对浓度≤1×10^7cfu／ml的E．coli液在24h内杀灭率达到99．5％。透射电镜结果显示，与奥氏体抗菌不锈钢作用后的E．coli细胞壁和细胞膜破裂，核区不明显；作用后的菌液中可溶性蛋白质含量增加；实验中未检测到有明显的菌体DNA断裂现象．结论：奥氏体抗菌不锈钢具较强的抗菌性能和广谱抗菌性。其作用机理可能为使菌体细胞壁和细胞膜因氧化而破裂，胞内可溶性蛋白漏出，最终导致菌死亡。     

Improved corrosion resistance and biofilm inhibition ability of copper-bearing 304 stainless steel against oral microaerobic Streptococcus mutans

304 stainless steel(SS) used as orthodontic wire during orthodontics faces the risk of microbiologically influenced corrosion(MIC) due to diverse flora environment. Hereinto, Streptococcus mutans(S. mutans)is the most important cariogenic bacteria. In this work, MIC behavior of a new 304-Cu SS in presence of S. mutans was studied by the observations using scanning electron microscopy(SEM) and confocal laser scanning microscopy(CLSM) including live/dead staining, extracellular polymeric substance(EPS)staining and pitting corrosion, electrochemical test, and X-ray photoelectron spectroscopy(XPS). Above results showed that 304-Cu SS possessed excellent biofilm inhibition ability and presented lower corrosion current density(icorr), larger polarization resistance(Rp) and charge transfer resistance(Rct) in the presence of S. mutans, indicating that 304-Cu SS had a better MIC resistance against S. mutans. It was further affirmed by XPS results that the presence of Cu-oxide in passive film of 304-Cu SS inhibited the formation of biofilm.     

Corrosion of a stainless steel handrail

AISI 304 and 304L stainless steels are “workhores” grades of austenitic stainless steel frequently used in architectural applications, as well as in cookware, appliances, and numerous other applications where resistance to corrosion is required. This paper examines a corrosion failure (the appearance of rustlike stains on the surface) of a 304 stainless steel handrail that appears to have occurred as a result of contamination during the fabrication process.     

Preliminary histological study of connective tissue response to Zinalco and stainless steel 316L implants after 120 days

Circular plates of Zinalco alloy (80 wt% Zn, 1.5 wt% Cu, 18.5 wt% Al) and stainless steel (SS) 316L were implanted in 12 female Wistar rats subcutaneously and intramuscularly to compare organism response, 120 days after implantation. The tissues surrounding the implants were analysed employing hematoxilin and eosin (H–E) and Gallegos trichromic techniques (GTT). Findings indicate that the reaction to Zinalco alloy was similar to the reaction to SS 316L. The Zn, Al and Cu concentrations in blood were measured, without evidence of any alteration due to implants. The presence and distribution of Zn, Al and Cu components of Zinalco alloy were detected in tissues by energy dispersive X-ray microanalysis. © 1998 Chapman & Hall.     

Electrochemical study of hydroxyapatite coatings on stainless steel substrates

Hydroxyapatite coatings were synthesized electrochemically onto stainless steel. In this study, the composition and morphology of the coatings changed with the deposition and sintering conditions. The electrolyte was kept close to the composition of simulated body fluid with an adjusted pH of 8.0. Deposition temperature affected the purity of the deposits with higher temperatures (65 °C) giving better coatings. The sintering techniques were also shown to affect the deposits, with x-ray diffraction patterns showing well-defined peaks for hydroxyapatite when sintering under vacuum conditions. Coating density and corrosion resistance was improved when applying a double-layer coating technique versus a single-layer. Grain sizes were 30 to 40 nm even after sintering of these coatings in air. The formed coatings were characterized by powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and x-ray photoelectron spectroscopy.     

Microscopy and neutron diffraction study of a zirconium-8 wt% stainless steel alloy

The electrometallurgical treatment of zirconium-based and Zircaloy-clad spent nuclear fuels will yield a metal waste form. The baseline composition for the waste form is zirconium-8 wt% stainless steel (Zr-8SS). The microstructure of the Zr-8SS alloy has been studied by scanning electron microscopy, energy dispersive spectroscopy, and neutron diffraction. The phases present in the as-cast alloy include Zr(), Zr₃(Fe,Ni), Zr₂(Fe,Ni), Zr₂(Fe,Cr), and Zr(Fe,Cr)₂; a solidification sequence has been proposed to explain the formation and morphology of these phases. Alloy phase stability has been studied by thermal aging at 780°C for periods up to 30 days. The phase changes that occur during thermal aging include an increase in Zr₃(Fe,Ni) and a decrease in Zr₂(Fe,Ni) content; reaction mechanisms have been proposed to explain these changes. The lattice parameters of alloy phases have been determined by neutron diffraction and found to be in agreement with those previously reported for similar phases. This study of alloy microstructures is the first step towards understanding the actinide and fission product distribution and predicting the corrosion behavior of the Zr-8SS metal waste form.     

Interface study for stainless steel fibre-reinforced aluminium matrix composite

Regular interface zones with uniform thickness in AISI 304 stainless steel-reinforced aluminium-matrix composite have been obtained using a vacuum high-pressure diffusion-bonding technique. Extensive and intensive experiments were performed to examine the growth of interfacial compounds with the variation of hot-pressing time and temperature. In the initial stage, the overall growth rate of the interface was found to follow a parabolic law. After a certain diffusion time, the interface growth rate fell behind that predicted by the parabolic law. A modified parabolic law has been established to explain the deviation and proved to be a better model to fit the experimental data. An activation energy of 152 kJ mol^-1 was found, which was somewhat lower than that obtained by previous work. The lower value of activation energy is attributed to the pressure (70 MPa) applied during hot pressing. Energy dispersive spectroscopic analysis and microhardness measurement indicated that the interface zone consists of a mixture of intermetallic compounds Fe(Cr, Ni)Al₂, Fe(Cr, Ni)Al₃ and (Fe, Cr, Ni)₂Al₇. This revised version was published online in November 2006 with corrections to the Cover Date.     

Texture in stainless steel welds: an ultrasonic study

We studied texture effects in five AISI-316 stainless-steel welds. We measured nine independent ultrasonic velocities along the weld's principal axes. These velocities reveal a strong texture different from the 0 0 1 fibre-type usually attributed to these materials The texture is independent of delta-ferrite content and must contain a strong 110 component related to the f c c monocrystal elastic constantC=(C ₁₁–C ₁₂)/2. A postulated ideal (0 0 1) [1 1 0] plate-type texture explains the range of measured longitudinal and transverse sound velocities, but not their detailed values.     

Chi-phase precipitation in a duplex stainless steel

The aim of this study is to investigate the precipitation of intermetallic phases, especially the chi-phase, in a 45N (type UNS S31803) duplex stainless steel through aging heat-treatments carried out at 700 and 750 °C. Two intermetallic phases are detected: chi (χ) and sigma (σ). The χ-phase precipitates at ferrite/ferrite grain boundaries prior to the σ-phase precipitation, which occurs preferentially at ferrite/austenite interfaces and at ferrite/ferrite grain boundaries. The σ-phase precipitation is a eutectoid type reaction of ferrite leading to σ-phase phase and austenite. The χ-phase is consumed in the σ-phase precipitation after becoming completely surrounded by both the σ-phase and the newly formed austenite.     

Failure of a braided stainless steel hose connector

Flexible water hoses are used as line connections from water supply plumbing to fixtures and appliances. The design configuration of these hoses varies; however, a common design involves an elastomeric liner surrounded by an outer reinforcement of braided stainless steel wire. These hoses are subject to rupture in service, traceable to the fracture of the braided wire reinforcement. The mechanism of failure involves localized corrosion of the stainless steel wire braid, a condition arising from the presence of water exterior to the hose. The following case of a ruptured water hose demonstrates this condition.     

Fracture toughness of a welded duplex stainless steel

The present work includes fracture toughness testing on 30 and 50 mm thick duplex stainless steel 2205 (22% Cr, 5.5% Ni, 3% Mo, 0.15% N). Base metal and submerged arc weldments (SAW) at subzero temperatures have been tested using full size three point bending. The evaluation of the results has been carried out using J-integral calculations and correlations to Charpy impact values. It is shown that the temperature dependence of the fracture toughness can be described by a transition temperature curve, the master curve. The reference temperature was evaluated to −143 and −101 °C for base and weld material respectively.     

Recovery of a creep-deformed Type 316 stainless steel

The recovery of the dislocation structures produced in a Type 316 steel during creep has been examined by annealing over a range of temperatures and times, both in the presence and in the absence of stress. The influence of dislocation recovery on subsequent reloading behaviour has also been examined.Initial dislocation recovery occurs rapidly but the rate of recovery subsequently decreases as precipitate effects become more important. Dislocation recovery in the early, rapid stage appears to be controlled by vacancy diffusion between the dislocation links. The application of stress during recovery leads to an enhancement of the recovery rate in agreement with the network coarsening model whilst the incremental strains observed on reloading after recovery correlate well with the changes in dislocation structure produced during the recovery periods.List of symbols and appropriate values l dislocation link length - D _s self diffusion coefficient - b Burgers vector (2.5×10^–1 m) - C _j equilibrium jog concentration - dislocation link tension - k Boltzman's constant (1.38×10^–23 J atom^–1 K^–1) - T absolute temperature - t recovery time - M mobility term - Z frictional term associated with particles - _d dislocation density determined from micrographs - N _d number of dislocation intersections on test line - p length of test line - S foil thickness - ¯l mean dislocation link length - _c mean intragranular particle (carbide) spacing - r ₀ mean intragranular particle radius at timet=0 - r _t mean intragranular particle radius at timet - D solute diffusion coefficient - B solubility of M₂₃C₆ in austenite - particle-matrix interface energy - atomic volume (10^–29m³) - change in dislocation density during recovery period - incremental strain associated with reloading after recovery period - K constant - dislocation density - ₀ dislocation density at timet=0 - _t dislocation density at timet - ₀ friction stress associated with particles - constant (1) - shear modulus - angle between dislocation segments as dislocation breaks through a particle - A 1 cos (/2) - E constant - creep rate - F Taylor factor - L mean slip distance of dislocations - rate of dislocation recovery - stress - _y yield stress - J strength coefficient - _p plastic strain     

Torsion response of a cracked stainless steel shaft

Pump shafts used for power generation are susceptible to fatigue cracking while often in near-continuous operation. Technology based on torsional vibration is under development for condition-based assessment of shaft health. The focus of this paper is on the relationship between a crack, which propagated due to bending loads, and the torsional stiffness of the shaft. An analytical method to determine the compliance associated with a crack has been implemented for a semi-elliptical surface crack. A 3-D finite element model of a shaft section with a crack has also been used to predict the effect of a crack on stiffness. Fatigue cracks were seeded in shafts on a three-point bend apparatus. A benchtop test rig was constructed to evaluate the torsional natural frequencies of a cracked shaft system. Quasistatic torsional stiffness tests indicated that crack closure has an effect on the results. A torsional finite element model of the benchtop test rig indicates that the first torsional natural frequency is reduced by the propagation of a crack. The reduction in torsional stiffness of the shaft inferred from the natural frequency results is in reasonable agreement with the quasistatic results and the model predictions.     

Plastic collapse of a stainless steel pressurized tube

The failure of a stainless steel tube which conducted oil at 300 °C has been analysed. The fracture surface of the broken tube was studied in the scanning electron microscope and the fracture mechanism found was the nucleation, growth and coalescence of voids. This mechanism is characteristic in materials plastically deformed before failure. Specimens for metallographic examination were cut from the damaged tube and from an intact tube to analyse both microstructures. No significant changes which could justify a microstructure’s embrittlement were detected. Hardness measurements were performed on the damaged and intact tubes. The broken tube was harder than the intact tube due to plastic deformation accumulated during failure. The pressure which is necessary to reach this hardening was analysed by the deformation theory of plasticity and it was found this pressure is close to that corresponding to the plastic instability. Consequently, the most plausible hypothesis of failure was due to an over-pressure which leads to the tube’s plastic collapse.