Bare Stainless Steel Surface Research Articles

Signal enhancement in laser diode thermal desorption-triple quadrupole mass spectrometry analysis using microwell surface coatings.

Laser-diode thermal desorption (LDTD) is an ionization source usually coupled to triple quadrupole mass spectrometry (QqQMS) and specifically designed for laboratories requiring high-throughput analysis. It has been observed that surface coatings on LDTD microwell plates can improve the sensitivity of the analysis of small polar molecules. The objective of the present study is to understand and quantify the effect of microwell surface coatings on signal intensity of small organic molecules of clinical, environmental, and forensic interest. Experiments showed that the peak areas of diclofenac, chloramphenicol, salicylic acid, and 11-nor-9-carboxy-Δ9 -tetrahydrocannabinol obtained by LDTD-QqQMS increased by up to 3 orders of magnitude when using microwells coated with ethylenediaminetetraacetic acid (EDTA). Tests with different chelating agents and polytetrafluoroethylene as microwell surface coatings showed that nitrilotriacetic acid gave significantly higher peak areas for five out of the nine compounds that showed signal enhancement using chelating agents as coatings. Scanning electron microscopy studies of EDTA-coated and uncoated microwells showed that analytes deposited in the former formed more uniform and thinner films than in the latter. The enhancement effect of surface coatings in LDTD-QqQMS was explained mainly by the formation of homogenous and thinner layers of nanocrystals of analytes that are easier to desorb thermally than the layers formed when the analytes dry in direct contact with the bare stainless-steel surface. Chemisorption of some analytes to the stainless-steel surface of the microwell plate appeared to be a minor factor. Surface coatings widen the number of compounds analyzable by LDTD-QqQMS and can also improve sensitivity and limits of detection.

Fabrication of self-cleaning superhydrophobic surface on stainless steel by nanosecond laser

Microstructures of stainless steel surfaces were textured by nanosecond laser. The surface morphology and hydrophobic properties of the stainless steel surfaces were measured by scanning electron microscope (SEM), OCA20 contact angle measuring instrument testing, respectively. It was found that the surfaces of the modified stainless steel achieved superhydrophobicity heated by a drying oven, the static contact angle reached 152 ± 1.3°. Microstructure and chemical elements of superhydrophobic surface modified by nanosecond laser were analyzed. Moreover, the contact angle about different temperature of droplets were studied on bare stainless steel surface and laser modified surface. The laser-modified superhydrophobic surfaces had been found to have good self-cleaning properties.

On the quenching of stainless steel rods with a honeycomb porous plate on a nanoparticle deposited surface in saturated water

Quenching of a stainless-steel rod with a porous ceramic structure, i.e. honeycomb porous plate (HPP), attached to its lower surface was investigated in distilled water under saturated conditions at atmospheric pressure. The experiments were performed on bare surface (BS) and on a TiO2 nanoparticle-deposited surface (NPDS). When the HPP was attached, the quenching rate increased significantly on both tested surfaces. The quench time for the NPDS with the HPP was 28-times shorter than that for the bare stainless-steel surface. The results suggested that the combination of the HPP ability to transport water to the heat-transfer surface by capillary action, and the increase of surface roughness, capillarity and wettability properties by the deposited nanoparticle layer were responsible for the enhancement obtained.

Protein-adsorption and Ca-phosphate formation on chitosan-bioactive glass composite coatings

In the last years, chitosan-bioactive glass (BG) composites have been developed and investigated as bioactive coatings for orthopedic applications. The increase of bioactivity occurs due to the stimulation of calcium-phosphate/hydroxyapatite formation on the surface while the coating is degrading. In the present work, protein adsorption and its influence on calcium-phosphate precipitation was studied for the first time on such composite coatings. The experiments involved coating of 316L stainless steel substrates with chitosan (Ch) and chitosan-bioactive glass (Ch-BG) and immersion of the coated samples in two different bovine serum albumin (BSA) containing solutions, namely DI H2O (with pH adjusted to about 7.2 with diluted NaOH) and simulated body fluid (SBF). In order to investigate the influence of protein adsorption on calcium-phosphate precipitation, samples were also immersed in DI H2O and in SBF without BSA. Samples were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Surface analysis revealed that adsorption of BSA takes place on all studied samples and that protein adsorption is influenced by the presence of Ca2+ and PO43− ions. Bioactivity in the form of hydroxyapatite pre-stage formation is significantly increased on Ch-BG composite coating as compared with bare stainless steel surface. However, calcium-phosphate precipitation in SBF is reduced by the presence of BSA.

Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces.

Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface.

Protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating characterized using quartz crystal microbalance

The protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating (Dursan®) were compared to that of an amorphous fluoropolymer (AF1600) coating and bare 316L grade stainless steel by studying non-specific adsorption of various proteins onto these surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D). A wash solution with nonionic surfactant, polyoxyethyleneglycol dodecyl ether (or Brij 35), facilitated 100% removal of the adsorbed bovine serum albumin (BSA), mouse immunoglobulin G (IgG), and normal human plasma proteins from the Dursan surface and of the adsorbed normal human plasma proteins from the AF1600 surface, whereas these proteins remained adsorbed on the bare stainless steel surface. Mechanical stress in the form of sonication demonstrated durability of the Dursan coating to mechanical wear and showed no negative impact on the coating's ability to prevent adsorption of plasma proteins. Surface delamination was observed in case of the sonicated AF1600 coating, which further led to adsorption of normal human plasma proteins.

QCM-D Study of β-casein on Silicate-PEG Surfaces

Nonspecific protein adsorption generally occurs on any solid surfaces and usually has adverse consequences. Adsorption of proteins onto a solid surface is believed to be the initial and controlling step in biofouling. Surfaces modified with end-tethered poly(ethylene glycol) (PEG) have been shown to be protein-resistant to some degree. In this study, the adsorption of s-casein was performed on several surfaces where PEG was tethered onto stainless steel by silicate. Protein adsorption was also performed on the bare stainless steel (SS) surface for comparison. The adsorption was conducted at 23 and 40°C and pH 7.2. In situ Quartz Crystal Microbalance/Dissipation (QCM-D) was used to determine PEG adsorption kinetics, plateau PEG chain densities, protein adsorption kinetics and plateau protein adsorbed quantities. The results showed that the presence of PEG molecules reduced the adsorption of s-casein, more than 50% than that on the bare SS surface. Interestingly, the adsorption of s-casein on the PEG surfaces at 40°C was much lower than that at 23°C.

Preparation of diamond like carbon thin film on stainless steel and its SEM characterization

We report the formation of a very smooth, continuous and homogeneous diamond-like carbon DLC thin coating over a bare stainless steel surface without the need for a thin Si/Cr/Ni/Mo/W/TiN/TiC interfacial layer. As confirmed by the field-emission scanning electron microscopy, good adhesion is achieved as characterized by (i) the formation of a smooth, continuous film with no pores, (ii) a significant reduction of oxygen in the interfacial layer, and (iii) the development of rich carbon content at the top surface. Thickness measurements by cross-sectional secondary-emission microscopy showed that the DLC coating is essentially a 2-dimensional material.

Electrochemically deposited poly(ethylene glycol)-based sol–gel thin films on stainless steel stents

Poly(ethylene glycol) (PEG) was modified with 3-isocyanatopropyltriethoxysilane (IPTS) to obtain PEG-disilane. This monomer was electrochemically polymerized and deposited onto a stainless steel surface to form a thin PEGylated sol–gel film. The monomer was characterized by 1H-NMR and FTIR spectroscopy. The sol–gel film was characterized by absorption–reflection infrared spectroscopy (AR-FTIR), energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV), profilometry, scanning electron microscopy (SEM) and potentiodynamic polarization. AR-FTIR confirmed the formation of a polymer, while the stability of the polymeric film on stainless steel in buffer phosphate was studied by scanning electron microscopy (SEM). The polymer was successfully electrodeposited onto 316L coronary stents. Its flexibility was examined by dilating the coated stents and inspecting it by SEM. The hydrophilic, smooth PEGylated sol–gel coating significantly reduced the activation and adhesion of platelets as compared with the bare stainless steel surface. This coating, which can be applied to complex geometries, such as stents, is likely to serve as an excellent biomaterial.

Combination of Electrografting and Atom-Transfer Radical Polymerization for Making the Stainless Steel Surface Antibacterial and Protein Antiadhesive

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) or copolymerization of TBAEMA with either monomethyl ether of poly(ethylene oxide) methacrylate (PEOMA) or acrylic acid (AA) or styrene. The chemisorption of this type of polymer brushes onto stainless steel surfaces has potential in orthopaedic surgery. These films have been characterized by ATR-FTIR, Raman spectroscopy, atomic force microscopy (AFM), and measurement of contact angles of water. The polymer formed in solution by ATRP and that one detached on purpose from the surface have been analyzed by size exclusion chromathography (SEC) and (1)H NMR spectroscopy. The strong adherence of the films onto stainless steel has been assessed by peeling tests. AFM analysis has shown that addition of hydrophilic comonomers to the grafted chains decreases the surface roughness. According to dynamic quartz crystal microbalance experiments, proteins (e.g., fibrinogen) are more effectively repelled whenever copolymer brushes contain neutral hydrophilic (PEOMA) co-units rather than negatively charged groups (PAA salt). Moreover, a 2- to 3-fold decrease in the fibrinogen adsorption is observed when TBAEMA is copolymerized with either PEOMA or AA rather than homopolymerized or copolymerized with styrene. Compared to the bare stainless steel surface, brushes of polyTBAEMA, poly(TBAEMA-co-PEOMA) and poly(TBAEMA-co-AA) decrease the bacteria adhesion by 3 to 4 orders of magnitude as revealed by Gram-positive bacteria S. aureus adhesion tests.

Experimental Study on the Heat and Mass Transfer of Teflon-Coated Tubes for the Latent Heat Recovery

The heat and mass transfer on stainless steel and Teflon-coated tube surfaces in a steam-air mixture flow were experimentally studied to obtain design data for a heat exchanger to be used in the latent heat recovery from flue gases. The test section consisted of three horizontal tubes with a pitch of 67 mm. The diameter of the tubes was 25.4 mm, and the tube wall thickness was 1.2 mm. The steam-air mixture flowed vertically from top to bottom. The Teflon coating degraded the overall heat transfer coefficient by 19%, as compared to the bare stainless steel tube. The degradation of the overall heat transfer coefficient of the Teflon-coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude on heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers of Teflon-coated surfaces have a different trend compared to bare stainless steel surface in the higher Reynolds number of our test. The higher contact angle of the condensate on the Teflon-coated surface, about 25°, is the reason for the kind of trend observed.

테프론 코팅 전열관 표면으로의 열 및 물질 전달 특성에 관한 실험적 연구

The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section. 3-tubes are horizontally installed. and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.

Investigations of the Mechanism of Corrosion Inhibition by Polyaniline. Polyaniline-Coated Stainless Steel in Sulfuric Acid Solution

The objective of this work was to elucidate the mechanism by which polyaniline (PANI) films passivate stainless steel surfaces in highly corrosive solution. A variety of experimental methods, including measurements of the open-circuit potential, Auger depth profiling, and the scanning reference electrode technique (SRET), was used. These studies have shown that passivation is achieved because the oxidized and protically doped emeraldine-salt form of PANI holds the potential of the underlying stainless steel electrode in the passive region. Because of this electrostatic mechanism of corrosion inhibition, the entire stainless steel surface does not have to be coated with PANI in order to achieve passivation. Auger depth profiling experiments show that, in analogy to the case of a bare stainless steel surface whose potential is potentiostatically maintained in the passive region, the stainless steel surface beneath the PANI film is enriched in Cr after exposure to the solution. Finally, SRET was used to explore passivation of the stainless steel in regions exposed to solution by pinholes intentionally cut through the PANI film. SRET shows that the PANI film surrounding the pinhole can heal the stainless steel in the pinhole region. © 2001 The Electrochemical Society. All rights reserved.

Boronization study for application to large helical device

An experimental device named SUT ( SU rface modification T eststand) was constructed for a boronization study. An ultra high vacuum (UHV) condition, a changeable high temperature liner and in situ AES are three distinctive feature of the SUT device. Saturation density of oxygen atoms was as large as 1.2 × 10 17/cm 2 on a boronized surface, whereas 1.5 × 10 16/cm 2 on a bare stainless steel surface. It is found by AES analysis that the oxygen-contained layer was as thick as 50 nm from the top surface of the boron film. From such a large oxygen-saturation density, we expect that the oxygen-gettering ability of the boronized surface is likely to be maintained during one-day experiment of LHD. The oxygen-saturation behavior was quite similar between the boronized surfaces obtained with decaborane and diborane, which indicates that, as a working gas of the boronization, the decaborane works well compared with diborane, as far as oxygen gettering is concerned.

Effect of Gold Coating on Sorption Characteristics of CO, Sulphur, and Other Gases on Stainless-Steel Sheet

Auger electron spectroscopic observations of the vacuum-deposited gold surface in comparison with bare stainless-steel surface have been made under varying vacuum conditions. The C and O peaks for the gold surface were negligibly small whereas those for the bare surface were rather intense and increased with time of exposure to primary electron bombardment. Decrease of the sulphur peak with increase of C and O peaks was observed for the bare surface which suggests that the impurity sulphur located on the stainless steel surface is covered by an adsorbed CO layer. Sulphur is the dominant impurity on a stainless steel surface after 700 °C flashing, but a very weak sulphur peak is observed for the surface covered by approximately 10 layers of vacuum-deposited gold film. Migration of sulphur from a bare stainless-steel surface to the gold-covered part of the surface has also been observed as a function of temperature.