Polished Stainless Steel Substrates Research Articles

Techno-Economic Analysis of Beam-Down Solar Tower Secondary Reflectors

Beam-down solar towers are presented as an alternative to conventional solar towers that allow modular design, easily adaptable to industrial environments. Secondary reflectors are a key component in this type of configuration, due to the high concentration of radiation received from the solar field. The results of a technical and economic study of new secondary reflectors, based on a polished stainless-steel substrate with silver PVD coating and a system of protective layers, are presented and compared with aluminum reflectors, currently used in such configurations. For this, twelve different designs, grouped in three cases are simulated using ray tracing and finite elements. The results show that the steel reflectors reach lower temperatures compared to aluminum reflectors, allowing for greater durability. Additionally, the optical efficiency of the plant was determined, and it was estimated that steel reflectors can reduce the LCOH of the plant by approximately 3.5%.

Substrate dilution and interface structures of tungsten coating deposited by double-glow plasma surface alloying on stainless steel substrate

W-coating layers with varying thicknesses up to 10 μm were deposited by double-glow plasma surface alloying (DGPSA) on finely polished stainless steel (SS304L) substrates to investigate the influence of the substrate on both the W-coating and interface structures. The examination revealed substrate dilution and the presence of oxide crystallites, predominantly FeWO4 and WO2, at the interface between W and SS304L. These observations correlated with the occurrence of cracking and peeling-off of the W-coating. Both Cr and Ni showed decreased distribution in the interface layer compared to their distribution in the W-coating and SS304L substrate. In comparison, Fe demonstrated a more noticeable compositional gradient, decreasing monotonically from SS304L across the interface to the W-coating. The depth distribution of O indicated that its inclusions were influenced not only by DGPSA deposition but also by post-deposition ion-beam milling. Additionally, the presence of spherical particles directly on the substrate's surface provided evidence for surface alloying reactions, while the columnar grains within the interface oxide layer were associated with the texture features of the W-coating, as confirmed by X-ray diffraction and pole-figure measurements. These findings offer valuable insights into the surface alloying process facilitated by DGPSA and its potential for developing W-coatings tailored for plasma-facing applications.

Sol–gel derived highly hydrophobic Polystyrene/SiO2 spray coatings on polished stainless steel and textured aluminium substrates

ABSTRACT In this study, sol–gel derived spray coatings of highly hydrophobic nature consisting of polystyrene (PS) and SiO2 nanoparticles were developed on polished stainless steel 321 (SS) and textured 6061 aluminium (Al) alloy substrates. The micro-structures on the Al surface were created through ultraprecision machining, known as single-point diamond turning (SPDT) machining. The polished SS and micro-structured Al were coated with PS/SiO2 using a spray coating technique by maintaining a pressure of 4–5 kPa, and positioning the nozzle 20–30 cm away from the substrates. The textured surface of Al was characterised using coherent correlational interferometry (CCI). The PS modified SiO2 nanoparticles and their coatings were characterised using Fourier-Transform Infrared Spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM). The resulting coating exhibited a micro-nano hierarchical roughness due to the presence of SiO2 nanoparticles and their fine size clusters. The polished SS surface showed static water contact angles of 93.3° and 143.5° before and after coating, respectively. Similarly, the polished and coated structured Al surface exhibited water contact angles of 85.6° and 144.3° before and after coatings. Such coatings can exhibit a great potential particularly in the field of self-cleaning technologies.

Improvement of high current performance of Li ion batteries with TiO2 thin film anodes by transition metal doping

Radio-frequency magnetron sputtering technique was employed to deposit transition metal doped TiO2 thin film electrodes on polished stainless steel substrates. Rutile phase TiO2 films have been deposited with 6% and 10% Fe, Mn and Co doping and separate coin cell type Lithium Ion Batteries (LIB’s) have been prepared with these samples as anodes. LIB’s with the doped thin film samples have marked very high charge storage capacities at high current rates, which are in some cases better than that obtained with pristine TiO2 electrode. Further, among the three dopants the performance of the Fe doped samples are the best over a large no. of cycles. During the cycling test, 10% Fe doped TiO2 electrode has marked very high specific capacity of 0.524 mAh cm−2μm−1 after 1000 cycles at low current rate of 0.13 mA cm−2 and of 0.264 mAh cm−2μm−1 after 500 cycles even at high current rate of 1.3 mA cm−2. Increase in the current rate by 10 folds has not affected the specific capacity much, manifesting excellent response of the battery at high current rate. In the present study we have applied Fe, Co and Mn doping to TiO2 electrodes prepared under identical conditions and have compared their performances as anodes of thin film LIB’s in detail and thus the results would be very useful in technological realization of these anodes in practical LIB systems.

Экспериментальные исследования характеристик фотокатодов ультрафиолетового диапазона спектра

Photoemission cells with high sensitivity to photons in the ultraviolet (UV) range of the spectrum have a wide range of practical applications in accelerator technology and generators of ultrashort electromagnetic pulses in the microwave range. The potential benefits of using UV photocathodes in these areas of technology are determined by such a combination of their properties as high electrical strength and high quantum efficiency. The report presents the results of experimental studies of the characteristics of photocathodes based on magnesium-barium (Mg-Ba) alloys and cesium iodide (CsJ). Photocathodes were fabricated by thermal vacuum sputtering on polished stainless steel substrates. It is shown that the dielectric strength of vacuum gaps with UV cathodes is significantly higher than with antimony-cesium cathodes in the visible range of the spectrum (for CsJ cathodes – 2.5 times, for Mg-Ba cathodes – more than three times). The quantum efficiency of Mg-Ba cathodes is ~1% at a wavelength of 247 nm, and that of CsJ cathodes is 7.5% at a wavelength of 196 nm. The results of studies of the dynamics of a decrease in the quantum efficiency of photocathodes under repetitively pulsed irradiation with laser pulses with a fluence 6 μJ/cm2. The characteristics of photocathodes are compared from the point of view of their practical applications.

Microstructural study of Ni and Ni-20Cr particles plasma sprayed on stainless steel substrate at 300 ˚C

In thermal spray coatings, the bonding and adherence of the spray particles (called splats) to the substrate surface significantly influence the overall quality of the finished coating. In this study, both elemental Ni and Ni-20Cr powders were plasma sprayed onto polished stainless-steel substrates held at 300 ˚C. Splat formation for both feedstock materials was investigated and compared. Detailed studies of the microstructure of single splats as well as the splat-substrate interface were performed using scanning electron microscopy (SEM), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). The additions of Cr to nickel promoted improved adherence of the splat to the substrate and modified splat formation by improving wettability during spreading. More intriguingly, energy dispersive spectroscopy (EDS) mapping and line scans, performed on TEM cross-sections, revealed splat-substrate inter-diffusion and chemical inter-mixing. Of particular note, a ‘jet’ of iron/chromium-based material, arising presumably from the substrate, was noted to be intimately intermixed into the interior of the nickel splat.

Remarkably high capacity Li ion batteries with rf sputter deposited TiO2 thin film anodes on SS substrates

TiO2 thin film electrodes have been prepared using radio-frequency magnetron sputtering technique on polished stainless-steel substrates. Films with amorphous, anatase and rutile phases have been obtained by varying the preparation conditions and coin cell type Lithium Ion Batteries (LIB’s) have been prepared with these samples as anodes. During the cycling test, all the samples show a gradual increase in capacity with increasing no. of charging/discharging cycles after an initial decrease with the cell containing the rutile phase TiO2 showing the highest specific capacity of around 1.217 mAh.cm-2.μm−1 after 1000 cycles at a high current density of 0.127 mA.cm−2, which is better than any reported value so far. Structural and morphological investigations of the samples by various techniques show that a synergy between the deposited TiO2 film and the Fe2O3 layers present on the SS substrate alongwith an increase in porosity in the films during the charge–discharge cycling gives rise to the remarkably high capacity of the cells which increases gradually with cycling. The present study shows that LIB’s with composite TiO2/Fe2O3 anode having advantage of structural stability of TiO2 and better diffusion kinetics of Fe2O3 can be obtained by a simple, easily scalable, reproducible rf magnetron sputtering technique and specific capacities of the present LIB’s are comparable to or better than that obtained through much more complicated and multi-step chemical processes and hence the results are important for large scale technological applications.

Enhanced lithium intercalation and conduction in LiαFeTaxOyCz films by the addition of lithium oxides with an atmospheric pressure plasma jet

An enhancement of lithium ionic intercalation and conduction performance of lithiated-organo-iron-tantalum oxide (LiαFeTaxOyCz) films has been accomplished by the addition of organo-lithium oxides (LiOyCz) into organo-iron-tantalum oxide (FeTaxOyCz) films using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of lithium tert-butoxide [(CH3)3COLi] and tantalum ethoxide [Ta(OC2O5)5] precursors. The rapid deposition of LiαFeTaxOyCz films onto polished stainless steel substrates at short exposed durations of 38–41 s with an APPJ has been investigated. The APPJ-polymerized LiαFeTaxOyCz films have noticeable Li+ ionic intercalation/deintercalation performance at 200 reversible cycles in a 1-M LiClO4-propylene carbonate electrolyte as analyzed by both potential sweep and potential step in situ Li+ ionic intercalation. The Li+ ion intercalated and deintercalated charges are significantly improved from 5.70 and 5.20 mC/cm2 for FeTaxOyCz film to 8.11 and 7.51 mC/cm2 for LiαFeTaxOyCz films, respectively. The Li+ ionic conduction performance of FeTaxOyCz film is slightly enhanced from 107 × 10−10 to 118 × 10−10 S/cm for LiαFeTaxOyCzfilm, as verified by electrochemical impedance spectroscopy in the devices of polyethylene terephthalate (PET)/indium tin oxide (ITO)/NiOx/FeTaxOyCz/NiOx/ITO and PET/ITO/NiOx/LiαFeTaxOyCz/NiOx/ITO.

Effect of Surface Pre-Treatment on Adhesive Strength of Multi-Component Vacuum-Arc Coatings

The results of investigations of multi-component nanostructured coatings of (TiAlSiY)N/CrN type are presented. The influence of different variants of substrate surface pretreatment on adhesive strength and hardness of coatings was studied. Pre-treatment of samples was carried out in plasma of two-stage gas discharge according to various technological schemes. Except for ion-plasma purification, some samples were pretreated with a sublayer of chromium within 5 minutes. The coatings were formed by a vacuum-arc deposition method at simultaneous spraying of two cathode targets. The first cathode is made of chromium, and the second cathode is made of multicomponent Ti - Al - Si - Y alloy obtained by vacuum-arc remelting of powder mixture of the mentioned elements. The coatings were deposited on polished stainless-steel substrates at negative 280 V bias potential. The geometry of the unit and its elements, as well as technological characteristics of the processes of evaporation-condensation were selected so that at a speed of rotation of samples 8 revolutions per minute the formation of the coating with a total thickness of about 9.0 microns occurred in approximately 60 minutes. The analysis of the composition of the coatings shows that the content of elements in the coating differs greatly from the content of elements in the sprayed cathodes. The X-ray diffractometry has shown that all deposition modes are characterized by the formation of phases with cubic (fcc) crystal lattice in both phase layers of multilayer coatings. In the layers formed at spraying of TiAlSiY alloy, a multi-element disordered solid solution (TiAlSiY)N with a crystal lattice of NaCl type and a lattice parameter of 0.4241 nm, as well as chromium mononitride CrN with a lattice parameter of 0.4161 nm, is determined. It has been established that preliminary formation of a chromium sublayer on the substrate leads to significant changes in adhesive strength of multi-component coatings compared to coatings without a sublayer.

Enhanced spectral selectivity through the quasi-optical microcavity based on W-SiO2 cermet

Improving the spectral selectivity of solar absorbers under certain optical concentration could boom the photothermal conversion efficiency. Here, the spectrally selective absorbing coatings based on a novel quasi-optical microcavity structure are fabricated on the mechanically polished stainless steel substrates by magnetron sputtering. The enhanced spectral selectivity via improving the solar absorptance in quasi-optical microcavity–based absorbers is ascribed to the synergistic mechanisms of cermet and traditional metal–dielectric–metal structure absorptances. The spectrally selective absorbing coatings with optimized quasi-optical microcavity structure demonstrate an excellent performance with solar absorptance of 0.957, thermal emittance of 0.044 (82 °C) and superior thermal stability at 600 °C in vacuum. The suppressing heat loss without degraded solar absorptance is due to the better crystallization and the formation of α-W in infrared reflector layer upon annealing at this temperature. The total conversion efficiency of an ideal system using this coating from solar radiation to electricity would reach around 65% at 600 °C with the focus of 1000 suns.

Lithium intercalation and conduction in Fe-containing tantalum oxide films synthesized with an atmospheric pressure plasma jet

Lithium ionic intercalation and conduction performance of tantalum oxides films improved by adding with iron oxides using an atmospheric pressure plasma jet (APPJ) is investigated. Precursors [tantalum ethoxide, Ta(OC2H5)5]2] and ferrocene [Fe(C5H5)2] vapors are carried by argon gas, mixed by oxygen gas and injected into air plasma torch for rapid synthesis of organo-tantalum-iron oxides (TaFexOyCz) films onto the polished stainless steel substrate at a short exposed-duration of 35 s. The APPJ-synthesized TaFexOyCz films possess the prominent Li+ ionic intercalation performance for 200 cycles of reversible Li+ ionic intercalation and deintercalation in a 1 mol/L LiClO4-propylene carbonate electrolyte by switching measurements with a potential sweep from − 1.25 to 1.25 V at a scan rate of 40 mV/s. After 200 cycles of reversible Li+ ionic intercalation and deintercalation, the Li+ ions intercalated and deintercalated charges are respectively increased from 2.41 and 1.91mC/cm2 for TaOyCz film to 5.69 and 5.23 mC/cm2 for TaFexOyCz film. The Li+ ionic conduction performance of TaOyCz film is highly enhanced from 5.76 × 10−11 to 1070 × 10−11 S/cm for TaFexOyCz film, while proven by electrochemical impedance spectroscopy in the devices of polyethylene terephthalate (PET)/indium tin oxide (ITO)/NiOx/TaOyCz/NiOx/ITO and PET/ITO/NiOx/TaFexOyCz/NiOx/ITO.

Study of water droplet evaporation in a mini-channel with gas flow

A series of experiments was conducted to study the evaporation of single water droplets with volume of 80~150 μl on the polished stainless steel substrate in temperature range of the substrate surface of 25–80°C in 6 mm high mini-channel with gas flow and the Reynolds number of the gas flow within 0-2500. New data on the water drop evaporation depending on the temperature of gas were obtained. The shadow method was the main method of measurement. As a result of experiments the experimental dependences for evaporation were obtained, and the influence of the gas flow rate and temperature on the water drop evaporation was analyzed.

ZnO thin films on single carbon fibres fabricated by Pulsed Laser Deposition (PLD)

Single carbon fibres were 360° coated with zinc oxide (ZnO) thin films by pulsed laser deposition using a Q-switched CO2 laser with a pulse duration τ≈300ns, a wavelength λ=10.59μm, a repetition frequency frep=800Hz and a peak power Ppeak=15kW in combination with a 3-step-deposition technique. In a first set of experiments, the deposition process was optimised by investigating the crystallinity of ZnO films on silicon and polished stainless steel substrates. Here, the influence of the substrate temperature and of the oxygen partial pressure of the background gas were characterised by scanning electron microscopy and X-ray diffraction analyses. ZnO coated carbon fibres and conductive glass sheets were used to prepare photo anodes for dye-sensitised solar cells in order to investigate their suitability for energy conversion devices. To obtain a deeper insight of the electronic behaviour at the interface between ZnO and substrate I–V measurements were performed.

English

TiN coatings were deposited onto mirror polished stainless steel substrates by reactive DC magnetron sputtering using a pure Ti target and Ar+N2 atmosphere. The deposited TiN coatings were thermally treated in ambient air at temperatures ranging from 500 to 700°C for times between 1 and 16 h. The as-deposited and thermally treated coatings were characterized using glow discharge optical emission spectroscopy, x-ray diffraction and scanning electron microscopy. Titanium oxide layers were identified at the surface of thermally treated TiN coatings, which grow according to oxygen diffusion controlled parabolic time law. Phase composition of the oxide layers is found to depend strongly on temperature and exposure time. At low temperatures and shorter exposure times the oxide layers were found to be a mixture of anatase and rutile polymorphs of TiO2, while at high temperatures and longer exposure times the oxide layers consisted only of the rutile polymorph of TiO2. The results show that the microstructure of the oxide layers is porous and non-uniform across the oxide layer thickness. The porous microstructure is explained by the accumulation of nitrogen by short-range diffusion and transition into a gaseous state. Key words: TiN, coating, magnetron sputtering, rutile, thermal treatment, X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GD-OES).

Water droplet evaporation and dynamics in a mini-channel under action of the gas flow

An experimental setup was developed to study the vaporization and dynamics of liquid droplets, blown by the gas flow in a mini-channel. The shadow method was the main method of measurement; a drop was also observed from the top. A series of experiments was carried out with single water drops with volumes varying from 60 to 150 gl in the channel of 6 mm height on the polished stainless steel substrate. The experiments have resulted in the dependences of evaporation rate in the temperature range of the substrate surface from 25 to 70°C and Reynolds numbers of the gas flow from 0 to 2500. The advancing and receding contact angles were measured depending on the Re number of the gas flow. The gas flow rate at which the droplet motion over the substrate starts was determined depending on the surface temperature at different drop volumes.

Corrosion behaviors of TiN and Ti-Si-N (with 2.9 at.% and 5.0 at.% Si) coatings by electrochemical impedance spectroscopy

TiN and Ti-Si-N (2.9at.% and 5.0at.% Si) coatings were fabricated on the surface of polished Si (100) wafers and stainless steel substrates by cathodic arc ion plating. The XRD results showed that the preferred orientation of the TiN crystals changed from TiN (111) to TiN (200) with an increasing silicon content. The TiN coating exhibited a polycrystalline structure with an average grain size of approximately 18nm, while the Ti-Si-N coatings exhibited a nanocomposite structure of TiN nanocrystals embedded in amorphous Si3N4. In electrochemical impedance spectroscopy (EIS) tests, the amorphous Si3N4 phase distributed on the boundaries of the Ti-Si-N (5.0at.% Si) coating and acted as an effective barrier layer against the penetration of the corrosion solution, which resulted in better corrosion resistance compared with TiN and the lower-Si-content Ti-Si-N coating (2.9at.% Si). Immersion tests and surface morphology observations of the samples after corrosion were also carried out to investigate the corrosion mechanism and behaviors of TiN and Ti-Si-N composite coatings.

Friction and Slip Property Investigation of Nanostructured Metal Surface Coatings

In this study authors tests whether on inclined plane principle based simple experimental slip property estimation device which is modified with optical sensors for sample sliding time measurements can be effectively used for surface static sliding friction coefficient (COF) and dynamic slip property investigation. Parameters measured with the device allows to compare how different types of surface treatments (including nanostructured coatings) influence surface tribological parameters thus allowing to determine most efficient treatment technology. In order to verify slip property estimation device effectiveness in real life situation prototype was fabricated and experiments with 5 samples (1 polished stainless steel sample and 4 titanium-containing nanocoatings sputtered on same polished stainless steel substrates) were formed. Collected experiment data approved that such device can be effectively used for both COF and dynamic slip property investigation.

Effect of splat morphology on the microstructure and dielectric properties of plasma sprayed barium titanate films

In the thermal spray process, the film is built up by impingement of molten droplets onto substrate. Splats are created by flattening and spreading of the impacting droplets. Splat morphology can determine the microstructure, physical and mechanical properties of the coating. In this study, BaTiO3 films were deposited onto a mirror polished stainless steel substrates kept at three different temperatures (25, 300 and 600°C). At the elevated temperatures, the substrate surface topography and the desorbtion of adsorbates and condensate at the substrate surface are two important factors which change the morphology of the individual splats, from splash morphology to disk-like shape. Splat morphology can determine deposit microstructure and improve the coating properties. The morphology of individual splats and the films were studied using scanning electron microscopy. Phase formation of the films was analyzed by X-ray diffraction. The surface topography of the substrates with different temperatures was analyzed using atomic force microscopy. Furthermore, X-ray photoelectron spectroscopy was performed to determine the chemical compositions of the surface substrate. Results indicated that the porosity in the film produced at room temperature was higher than that in the film deposited on the heated substrates. Also, the dielectric coefficient of the films was increased by decreasing the common defects from 120 to 505 for film deposited on as-received and heated substrates, respectively.

Enhanced Thermal Stability of W‐Ni‐Al2O3 Cermet‐Based Spectrally Selective Solar Absorbers with Tungsten Infrared Reflectors

Solar thermal technologies such as solar hot water and concentrated solar power trough systems rely on spectrally selective solar absorbers. These solar absorbers are designed to efficiently absorb the sunlight while suppressing re‐emission of infrared radiation at elevated temperatures. Efforts for the development of such solar absorbers must not only be devoted to their spectral selectivity but also to their thermal stability for high temperature applications. Here, selective solar absorbers based on two cermet layers are fabricated on mechanically polished stainless steel substrates using a magnetron sputtering technique. The targeted operating temperature is 500–600 °C. A detrimental change in the morphology, phase, and optical properties is observed if the cermet layers are deposited on a stainless steel substrate with a thin nickel adhesion layer, which is due to the diffusion of iron atoms from the stainless steel into the cermet layer forming a FeWO4 phase. In order to improve thermal stability and reduce the infrared emittance, tungsten is found to be a good candidate for the infrared reflector layer due to its excellent thermal stability and low infrared emittance. A stable solar absorptance of ≈0.90 is demonstrated, with a total hemispherical emittance of 0.15 at 500 °C.

Observations and Mechanism of CaSO4Fouling on Hydrophobic Surfaces

Pool boiling of CaSO4 solution on prepared microscale and nanoscale hydrophobic titania–fluoroalkylsilane (TiO2–FPS) composite coatings on polished AISI304 stainless steel (SS) substrates was carried out to evaluate the antifouling behavior of these surfaces. Lower fouling resistance and looser, slender, and larger CaSO4 crystals on hydrophobic TiO2–FPS coatings were observed compared to those on the TiO2 coatings and SS surfaces. The colloidal interaction energies between crystalline particles and coated surfaces were analyzed by using the extended Dejaguin– Landau–Verwey–Overbeek (XDLVO) theories to explore the possible mechanism of inhibition of fouling. The results of the XDLVO analyses generally agree to the experimental observations. The Lewis acid–base component contributes most of the total XDLVO interaction energy. Low surface free energy and electron donor component of heat transfer surface lead to a low fouling resistance and a small initial deposition rate of CaSO4 fouling. On the basis of the...