Stainless Steel Grid Research Articles

First air-tolerant effective stainless steel microbial anode obtained from a natural marine biofilm

Microbial anodes were constructed with stainless steel electrodes under constant polarisation. The seawater medium was inoculated with a natural biofilm scraped from harbour equipment. This procedure led to efficient microbial anodes providing up to 4 A/m 2 for 10 mM acetate oxidation at −0.1 V/SCE. The whole current was due to the presence of biofilm on the electrode surface, without any significant involvement of the abiotic oxidation of sulphide or soluble metabolites. Using a natural biofilm as inoculum ensured almost optimal performance of the biofilm anode as soon as it was set up; the procedure also proved able to form biofilms in fully aerated media, which provided up to 0.7 A/m 2. The current density was finally raised to 8.2 A per square meter projected surface area using a stainless steel grid. The inoculating procedure used here combined with the control of the potential revealed, for the first time, stainless steel as a very competitive material for forming bioanodes with natural microbial consortia.

Impact of PEF treatment inhomogeneity such as electric field distribution, flow characteristics and temperature effects on the inactivation of E. coli and milk alkaline phosphatase

Abstract High intensity pulsed electric field (PEF) treatment was investigated focusing on the alteration of electric field distribution, flow characteristics and temperature distribution due to the modification of the treatment chamber. The aim was the improvement of the effectiveness of microbial inactivation of E. coli and to reduce the PEF impact on alkaline phosphatase (ALP) activity in raw milk. Mathematical simulation of the PEF process conditions considering different treatment chamber setups was performed prior to experimental verification. Finally the impact of the treatment chamber modifications on microbial inactivation and enzyme activity was determined experimentally. Using a continuous flow-through PEF system and a co-linear treatment chamber configuration the insertion of stainless steel and polypropylene grids was performed to alter the field strength distribution, increase the turbulence kinetic energy and improve the temperature homogeneity. The Finite Element Method (FEM) analysis showed an improved electric field strength distribution with increased average electric field strength and a reduced standard deviation along the center line of the treatment zone indicating a more homogenous electric field. The velocity profile was improved resulting in an increase of turbulence kinetic energy due to the insertion of the grids. As revealed by mathematical modeling, the temperature of the liquid was decreased, and formation of temperature peaks was avoided. Measured inactivation of heat sensitive alkaline phosphatase (ALP) was reduced from 78% residual activity to 92% after PEF treatment and it could be shown that thermal effects and temperature peaks have been the main reason for enzyme inactivation due to PEF. At the same time, an increase of microbial inactivation of 0.6 log–cycles could be determined experimentally due to the modification of the treatment chamber design. Industrial relevance The application of pulsed electric field as a non-thermal pasteurization technology requires an accurately defined treatment intensity followed by a predictable microbial inactivation. Unavoidable thermal effects occurring during PEF treatment due to ohmic heating have to be minimized to assure the retention of heat-sensitive nutrients and bioactive compounds. The presented investigations contribute to the fulfilment of these requirements for further successful industrial implementation of the PEF technology such as the selective inactivation or retention of enzyme activity in liquid food systems.

Experimental evidence of reduced sticking of nanoparticles on a metal grid

Filtering of NaCl, CaCl 2, (NH 4) 2SO 4 and NiSO 4 aerosol particles 7–20 nm in diameter by a stainless steel grid was studied in order to find out if there is perfect sticking or partial rebound. Our experiment used particles from a spray-drying process, the majority of which were electrically neutral. Penetration through the grid was measured by comparing the concentration downstream of the grid with the upstream concentration under otherwise identical conditions. Size selection was done with a scanning mobility particle sizer (SMPS). Filter penetration P as function of the particle diameter d p was expressed by - ln ( P ( d p ) ) = C d p - x . The values of x determined were smaller than the theoretical value of 1.29, indicating enhanced penetration of small particles and deviation from the classical filtration model. Because of possible systematic errors in the size selection, we focus on the differences of x from material to material, which indicate different sticking probabilities. We apply a statistical test, which yields a 90% confidence level for the result. There is a sticking probability of <100% at least for NaCl particles and even more so for NiSO 4. This result is in contrast to former findings using metal and/or charged particles, and we speculate that the discrepancy is due to the smaller Hamaker constant of salts and that particle charge is important for the sticking probability.

Growth and Optical Properties of Sallow-Like Hierarchical SnO&lt;SUB&gt;2&lt;/SUB&gt; Nanostructures

Novel self-organized hierarchical SnO2 nanostructures have been successfully prepared by vapor phase transport with the assistance of a stainless-steel grid at 950 degrees C. Scanning electron microscopy shows that the synthesized product displays interesting sallow-like morphology, in which numerous secondary branches (beak-like nanowires) are grown randomly around the main stems (microwires). Transmission electron microscopy analysis indicates that the branches grow along a direction of [100] and the beak is formed with the growth direction switching to [110]. A room temperature photoluminescence spectrum of the present SnO2 nanostructures shows a strong emission at 572 and 604 nm(-1).

Synthesis and field emission of two kinds of hierarchical SnO 2 nanostructures

Novel self-organized hierarchical SnO 2 nanostructures have been successfully prepared by vapor phase transport with the assistance of a stainless steel grid at 950 ∘C. Scanning electron microscopy shows that the two kinds of products synthesized display interesting sallow-like and fishbone-like morphologies, in which numerous secondary branches are grown randomly around the main stems. Transmission electron microscopy analysis indicates that SnO 2 nanowires are single crystals. Field emission measurements of these nanostructures showed a high emission current density and low turn-on field of 1.88 and 2.36 V μm −1, which is comparable to that of one-dimensional SnO 2 nanostructure. We also studied the influence of gas adsorption on the field emission properties of hierarchical SnO 2 nanostructures. The good performance for field emission makes the hierarchical SnO 2 nanostructures promising candidates for further applications in field emission microelectronic devices.

Electrochemical study of indoor atmospheric corrosion layers formed on ancient iron artefacts

Several indoor atmospheric corrosion layers (0–800 years old) were selected from different localisations in France. Each sample was scrapped from its iron substrate. The resulting powder was mixed with graphite in appropriate proportions and the mixture was pressed onto a stainless steel grid to constitute a composite electrode. The electrochemical responses of the different samples were recorded under galvanostatic regulation, in a near-neutral pH-buffered NaCl solution at 25 °C. The E– t reduction curves allowed the determination of two characteristic parameters, E τ/2 , the potential value obtained at half the transition time, and Q τ , the coulombic charge obtained at the end of the reduction. The diminution of E τ/2 and Q τ with the age of the corrosion layer showed that the “reduction reactivity” decreases with time, suggesting a progressive stabilisation of the corrosion layer. In a second part of the work, we synthesised several common ferric or ferrous/ferric products (goethite, lepidocrocite, magnetite, maghemite, ferrihydrite) and compared their reduction responses (product alone or mixture of 2 or 3 products) to those of corrosion samples.

Polypyrrole films electrosynthesized on stainless steel grid from saccharinate aqueous solution and its behaviour toward acetone vapor

The electrochemical behaviour of stainless steel electrode in 0.1 M sodium saccharinate solution in the absence and the presence of the monomer were investigated using several electrochemical techniques such as cyclic voltammetry, galvanostatic and potentiostatic. The XPS analysis was used to study the elementary composition of the obtained polymer and to estimate the doping level of the PPy obtained under this electrolytic conditions. Moreover, the characterization of the coating was achieved by SEM, IR and Raman. In this context, samples of PPy in oxidized and reduced state synthesized galvanostatically on stainless steel grid were used to investigate the behaviour of the polymer toward acetone vapor.

Adaptation of a four-arm olfactometer for behavioural bioassays of large beetles

We adapted a four-arm olfactometer (55 × 55 × 5.5 cm) for bioassays of large insects and its usefulness was evaluated by testing the responses of three beetles, the palm weevil Rhynchophorus palmarum (L.) (Coleoptera: Curculionidea) and two Dynast scarabs Strategus aloeus (L.) and Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae) to plant odours and aggregation pheromones. This olfactometer was coupled to a volatile delivery system dispensing highly volatile semiochemicals at constant concentrations. We materialized airflows in the olfactometer by discolouring sensitive papers with acid vapours under various conditions (air straighten by stainless steel grids in inputs and output, 500 ml/min per arm) to visualize air turbulence and to test air-tightness. The volatile delivery system can be used to mix and dispense a broad range of concentrations of semiochemicals in air from diluted aqueous solutions. It was calibrated by measuring the release of the pheromone using solid phase-microextraction (SPME). Dose-response curves to synthetic pheromone were obtained for O. rhinoceros of both sexes. Coupling the volatile delivery system to the fourarm olfactometer provided a system with which the responses of R. palmarum and S. aloeus to their synthetic aggregation pheromones and to natural plant volatiles could be readily observed and studied.

Preparation of Silicalite Membranes on Stainless Steel Grid Supports

Silicalite membranes have been prepared by seeded liquid-phase hydrothermal synthesis on alternative supports, namely, two types of stainless steel grids with opening sizes ranging from 2 to 5 μm. The influence of the gel composition, the use of surfactants, and the synthesis time have been studied. The silicalite membranes prepared on stainless steel grids were tested in the separation of n-/i-butane mixtures, showing performances which are comparable to those of good quality membranes prepared on conventional supports.

Patterned Growth of ZnO Nanorod Arrays on a Large-Area Stainless Steel Grid

Large-area ZnO nanorod arrays have been synthesized successfully on a stainless steel grid at a mild growth temperature of around 400 degrees C. The as-grown ZnO nanorods have uniform diameters of about 30-50 nm with approximately 5 nm tips. Patterned growth can be realized by engineering the shape of the grid in the growth. Photoluminescence demonstrates a sharp strong UV peak and a broad green band. The growth method provides a promising way of producing nanorod arrays with good controllability in patterns and morphologies, which will be critical in potential application such as high-efficiency filtering and catalysts.

Contribution and origin of H3O+ in the mass spectral peak at 19amu

Typically, the mass spectral peak observed at 19 amu in residual gas analyzers at very high vacuum (VHV) and ultrahigh vacuum (UHV) has been attributed to fluorine. Using Fourier transform mass spectrometry (FTMS), the presence of the hydronium ion H3O+ has been fully resolved from F+. Correlation of the mass 19 signals for a conventional quadrupole mass spectrometer (QMS) and the FTMS, positioned adjacent, unambiguously indicates hydronium as the source of mass 19. At partial pressures of H2O in the VHV range and higher there is sufficient density for the formation of the hydronium ion through ion–molecule interactions. Formation of the hydronium was found to directly correlate with the partial pressure of H2O. However, in a QMS, formation of H3O+ in UHV appears to occur principally by electron stimulated desorption (ESD). Dosing the system with hydrogen from 1L exposure to saturation (1×10−6Torr for 8h) was found to increase the H3O+ ESD yield detected by the QMS by as much as a factor of 10. The initial hydronium ESD cross section from a hydrogen saturated grid was estimated to be σ∼1×10−19cm2. In a separate experiment, time of flight–secondary ion mass spectrometry sputter yields from the stainless steel grid of a quadrupole mass spectrometer also showed small signals of H3O+, as well as its constituents, H+, O+ and OH+, but no F+.

Development of an H− ion source based on the electron cyclotron resonance plasma generator at CEA/Saclay

Electron cyclotron resonance (ECR) plasma generators have demonstrated their efficiency, reproducibility, and long lifetime for the production of light positive ions like protons or deuterons. These sources generally work in cw mode. A 2.45 GHz ECR test stand based on a pure volume H− ion production is currently under development. This negative ion source is working in pulsed mode, 1 ms at 10 Hz. The first H− ions have been observed at the beginning of 2002 with a poor efficiency. Only a few μA were produced. To avoid negative ions destruction by a nonabsorbed microwave close to the extraction aperture, a stainless steel grid was installed in the rectangular plasma chamber. As a result, the chamber is now effectively separated into two zones: the ECR plasma generator and the H− production zone. By plotting the extracted current versus the production zone length, the H− ion intensity reached more than 100 μA with the grid located 25 mm from the aperture. A voltage difference on the order of 10 V can be applied between the two parts of the plasma chamber in order to modify the electron energy entering the production zone.

Electron transfer between hydrogenase and 316L stainless steel: identification of a hydrogenase-catalyzed cathodic reaction in anaerobic mic

Electron transfer between the NAD-dependent hydrogenase from Ralstonia eutropha and AISI 316L stainless steel was studied with a view to identifying a possible role of hydrogenase in anaerobic microbially influenced corrosion (mic), as already suspected. A thin spectroelectrochemical cell was designed and qualified, taking great care to obtain a reproducible surface state of the stainless steel grid electrode. Successive electrolyses were performed at potential values in the range from −0.60 to −0.90 V(SCE), with different NAD + concentrations, and different hydrogenase activities. Hydrogenase significantly enhanced the charge consumed when NAD + was present in solution. In the absence of NAD + it exerted, on the contrary, a masking effect, like an inert protein. The charge consumed during each electrolysis was compared with the charge derived from the spectrophotometric monitoring of NADH formation. Depending on the potential value, hydrogenase predominantly catalyzed either the reduction of water to hydrogen, or the reduction of NAD + to NADH. The current due to the presence of hydrogenase and NAD + remained low according to corrosion moities, but it was demonstrated here that the presence of hydrogenase on the surface of stainless steel induces an effective hydrogenase-catalyzed cathodic reaction that must be taken into account in mic.

Strong low-frequency turbulence observed in presheaths

A noise whose frequency is from 0 to ωpi/10, where ωpi is the ion plasma frequency, is observed in presheaths in both sides of a plane stainless-steel mesh grid immersed in a uniform and unmagnetized plasma. To excite the noise, a negative dc voltage lower than −20 V is applied to the grid. The frequency spectrum of the noise is expressed with the Lorenz distribution a/(f2+fo2), where f is the frequency and a and fo are constants. The noise is found to propagate away from the grid with the speed of one-fifth of the ion-sound velocity. The noise is considered to be excited in the presheaths by counter-streaming ion-beams whose velocity are slower than the ion-acoustic velocity. The kinetic dispersion relation is solved numerically and results are compared with experimental findings.

Synthesis and characterization of MCM-41 coatings on stainless steel grids

Innovative structured catalytic packings have been prepared by in situ hydrothermal synthesis of mesoporous MCM-41 on stainless steel grid. After a one-step synthesis, the metal support was observed to be homogeneously covered by a dense layer (∼ 80 μm ) of the mesoporous material.

Copper reinforced catalysts on a heat-exchange surface for nitrobenzene hydrogenation to aniline

The methods of X-ray diffraction, mercury porosimetry, and electron microscopy are used to study the texture and phase composition of nickel–aluminum supports obtained by the sintering of nickel and aluminum powders reinforced by a stainless steel grid and distributed over a heat-exchange surface, as well as copper catalysts for nitrobenzene hydrogenation to aniline supported on these materials. The catalysts prepared using this procedure are active in this reaction and make it possible to carry it out without substantial overheatings of the surface.

Synthesis of multiwalled carbon nanotubes using methane/air diffusion flames

An experimental investigation has been conducted on the synthesis of multiwalled carbon nanotubes (MWCNTs) using methane/air laminar diffusion flames, with an emphasis on the effects of flame temperature and catalyst particle size on nanotube growth. The yield of MWCNTs occurred on a substrate consisting of a 0.4 mm Ni−Cr (60% Ni, 26% Cr, and 14% Fe) catalyst wire connected to a stainless steel grid. The self-formed catalyst particles in the flame were analyzed by energy dispersive X-ray to be mostly nickel oxide with some iron oxide. A high-resolution transmission electron microscope analysis indicates well-graphitized layers of MWCNTs consisting of continuous lattice fringes along the cylindrical section of the nanotube. We studied the effects of flame temperature on nanotube growth by changing the sampling location along the flame height and diluting methane with nitrogen. High temperature was found to favor the growth of large-diameter nanotubes, and nanotube growth was influenced by chemical species environment in the flame. Nitric acid treated Ni−Cr wire produced smaller sized catalyst particles that can be encapsulated within the nanotubes. The growth of well-aligned, bean-sprout-like bundles of nanotubes with catalyst particles pushed up at the tube top was found to occur: the mechanism of this unique synthesis is unknown and needs further study.

Ethylene flame synthesis of well-aligned multi-walled carbon nanotubes

A stainless steel grid baked by a propane–air premixed flame had iron, chromium and nickel oxide deposits on the grid surface. With this grid, entangled and curved shape multi-walled carbon nanotubes (MWNTs) were harvested from an ethylene–air diffusion flame with yield rate of 3 mg/min. Nitrogen addition to the flame was found to straighten the entangled tubes probably by lowering the flame temperature. A cobalt-electrodeposited stainless steel grid was finally applied to the nitrogen-diluted ethylene diffusion flame; well-aligned and well-graphitized carbon nanotubes consisting of 20 nm diameter and 10 μm long element tubes were obtained.

Silicon (110) grid for ion beam processing systems

Grids fabricated by anisotropically etching (110) silicon havebeen investigated for use in extracting and accelerating ions throughtheir apertures. The silicon grids provide stable ion beams, resulting ina life span that is five times that of conventional stainless-steel gridsof the same grid thickness, and large thickness for the same open areas.The silicon grids also have a big advantage because they do not experiencethe substantial plastic deformation that stainless-steel grids do. Inaddition, they provide a density of ions a few times higher thanconventional carbon grids, although their life span is shorter. Moreover,they can protect samples from being contaminated by impurities such asheavy metals contained in stainless steel. Therefore, silicon grids aresuitable for fabricating optical elements, such as microlenses and opticalfilms in optical microelectromechanical systems.

Synthesis of ZSM-5 coatings on stainless steel grids and their catalytic performance for partial oxidation of benzene by N 2O

The one step hydroxylation of benzene has been performed over structured catalytic bed made of ZSM-5 coatings grown by hydrothermal synthesis on stainless steel grids. The catalysts demonstrated a 97% selectivity towards phenol formation at benzene conversion of 11%. In addition of achieving the same reactivity as over the traditional zeolitic fixed beds, these new catalytic packings present several advantages gained from the special arrangement of the catalytic bed like low pressure drop, improved heat and mass transfer, and controlled hydrodynamics.