Surface Of Porous Stainless Steel Research Articles

Experimental study on electrical discharge machining of porous and pure 316L stainless steel

Porous metal materials are widely used in heat-absorbing, biomedical parts and other fields because of their excellent mechanical properties and biocompatibility. Further applications of porous metal materials are inseparable from secondary precision machining. However, traditional cutting methods tend to compromise the original porosity of the material surface. Electrical discharge machining (EDM) is a type of non-conventional machining method which is more preferable to overcome these defects. In the present study, the main target is to investigate the effect of four input electrical machining parameters (current, frequency, efficiency and gap voltage) on the five output responses (material removal rate (MRR), electrode wear, surface roughness (SR), noise and time consumption value of environmental particulate matter (PM2.5)) when electrical discharge machining porous 316L stainless steel and compared with that of pure 316L stainless steel. The Taguchi method was employed to determine the relationship between electrical discharge machining parameters and output responses. The analysis of variance (ANOVA) was used to evaluate the effect of input parameters on output responses. The effects of electrical machining parameters on above responses were analyzed by main effects, and the order of influence was obtained, respectively. Finally, the surface morphology was observed by scanning electron microscope (SEM), and the effect of electrical machining parameters on the characteristics and formation of machined surface of porous stainless steel was mainly analyzed.

Oxidation of porous stainless-steel coated with donor-doped SrTiO3 in anodic atmosphere of solid oxide fuel cell

This study evaluates the effect of donor-doped SrTiO3 (La0.2Sr0.8Ti0.9Ni0.1O3-δ, LSTN) coating on chromia growth on the surface of porous stainless steel (STS). During subsequent exposure to wet H2 atmosphere at 800 °C, the porous STS oxidizes, and its Ohmic resistance increases slowly for 300 h to an area-specific resistance (ASR) ∼2.5 mΩ cm2, but at a much slower rate does uncoated STS and to a much lower ASR than that of uncoated STS (∼17.9 mΩ cm2). The estimated parabolic rate constant indicates that the porous LSTN-coated STS may be used at temperature <680 °C for ∼10 y.

Facile surface modification of porous stainless steel substrate with TiO2 intermediate layer for fabrication of H2-permeable composite palladium membranes

ABSTRACTThe increasing demand in compact hydrogen separators greatly stimulated the investigation and utilization of composite palladium membranes. Porous stainless steel (PSS) tubes were chosen as substrate material in this study, and a novel process of carbon-assisted solid-state sintering was introduced to modify the PSS surface with a TiO2 layer. A Pd/TiO2/PSS membrane with a Pd thickness of 6 µm was successfully fabricated via electroless plating. Scanning electron microscopy (SEM), metallographic microscopy, X-ray diffraction and pore-size analyses were performed for material characterizations. As measured by H2/N2 single-gas testing, the fabricated Pd/TiO2/PSS membrane is permeable and selective to hydrogen, and it was stable during a time-on-stream of 100 h under 450°C.

Preparation of palladium/NaX/PSS membrane for hydrogen separation

Abstract Palladium (Pd) membranes on porous stainless steel (PSS) were prepared by electroless plating. An intermediate layer of NaX nanozeolite was employed to modify the pore size of the PSS support and improve the hydrogen permeability. NaX nanozeolites were synthesized using convectional hydrothermal method. The NaX intermediate layer was coated by vacuum-assisted method on the PSS surface. The structure and morphology of the prepared membranes were characterized using SEM, XPS and XRD analysis. Permeation measurements were conducted using H 2 , N 2 and mixture of H 2 /N 2 at different temperatures (350–450 °C), and trans-membrane pressures (4–8 bar). The results indicated that the permeability and hydrogen selectivity were increased by enhancement in temperature and pressure. The hydrogen fluxes in H 2 /N 2 mixtures were lower than those corresponding to pure hydrogen at the same partial pressures and temperatures. The obtained results suggests that the use of NaX nanozolite is an effective intermediate layer in Pd/PSS membranes for hydrogen separation.

Thin Pd membrane on a modified porous stainless steel tube: Al2O3 particle size selection strategy

Palladium (Pd) membranes for hydrogen separation were deposited on modified porous stainless steel (PSS) tubes using the electroless plating technique. This study explores the hydrogen permeance influenced by the effect of reducing the thickness of the Pd membrane using different sizes of Al2O3 particles, 10 and 1 µm, to modify the pores on the PSS surface. The pore size on the surface of the PSS tubes modified with 10 µm Al2O3 particles decreased from 10 ∼ 20 µm to less than 5 µm, while the surface of the PSS, modified by 1 µm Al2O3, was very dense and smooth. Generally, the supporting tubes with smaller pore size on the surface give thinner Pd membrane. The minimum thickness of a dense Pd membrane decreased from 35.1 to 16.2 µm when using 1 µm Al2O3 particles to modify the PSS tubes, but the maximum hydrogen permeance was enhanced from 15.3 to 34.7 m3/m2 h atm0.5 at 500°C by using 10 µm Al2O3 particles. This evidence demonstrated the hydrogen permeance has a trade-off between the porosity (effective passages) and thickness of the Pd membranes since both are influenced by the Al2O3 particle size used in the surface modification. These results suggested a promising and simple approach to produce a Pd membrane with high hydrogen permeance.

Design and synthesis of thin palladium membranes on porous metal substrate for hydrogen extraction

Membrane separation is regarded nowadays as a preferred method for production of purified hydrogen. Palladium (Pd) is an attractive membrane material due to its ability to dissociate molecular hydrogen into atoms. It is usually deposited on the porous substrate that can provide good mechanical support and reduce the thickness of the membrane for maximizing hydrogen permeability. Pd membrane used for hydrogen separation must be thin enough to increase hydrogen flux and reduce cost while remaining thick enough to retain adhesion, attrition resistance and mechanical integrity during high temperature cycles. In this paper, the progress of electroless deposition of Pd around the pore area at surface of porous stainless steel was recorded and a bridge structure that was formed during the membrane deposition around the pore area of the substrate was illustrated. After that, the porous substrate was modified using micro-or nano-size metal or metal oxide particles in order to reduce pore size in the substrate surface. The experimental results obtained from hydrogen permeation through the Pd membranes having the thickness from 400 nm to 18 μm built on both modified and original porous stainless steel substrates demonstrate that these thin membranes are solid and they can be used at the temperature of 550°C and hydrogen pressure difference of 3.447x105 Pa. The proposed processing will allow optimizing the design and fabrication of thin Pd membranes on different porous substrates for hydrogen separation.

Design and Synthesis of Thin Palladium Membranes for Hydrogen Separation

The progress of electroless deposition of palladium around the pore area at surface of porous stainless steel was recorded in order to understand membrane formation and to control the membrane quality. A bridge structure is formed during the membrane formation around the pore area of the substrate. The porous substrate was modified to be smooth using micro-or nano-size metal or metal oxide particles in order to make sure that palladium membrane is strongly supported by the substrate and as the result the membrane thickness can be further reduced. The experimental results obtained from hydrogen permeation through the palladium membranes having the thickness from 400 nm to 18 μm demonstrate that these thin membranes are solid and they can be used at the temperature of 550°C and hydrogen pressure difference of 350 kPa. The proposed processing will allow optimizing the design and fabrication of thin palladium membranes for hydrogen separation.

Controlling palladium nanowire size through electroless deposition process

An inexpensive electroless deposition technique has been used to build highly-ordered palladium nanowires on a porous stainless steel surface. The nanowire formation starts by aligning palladium nanoparticles in one direction, linking the nanoparticles so they become a nanowire bead by bead, ultimately forming a uniform wire. The diameter of the palladium nanowire can be controlled by the concentration of PdCl2 in the plating bath. The experimental results reported here are promising for developing desired palladium nanowires in potential engineering applications.