Resistance Of Substrates Research Articles

ZnO films on transferable and low thermal resistance graphite substrate grown by ultrasonic spray pyrolysis

ZnO thin films were deposited on graphite substrates by ultrasonic spray pyrolysis method with Zn(CH3COO)2·2H2O aqueous solution as precursor. The crystalline structure, morphology, and optical properties of the as-grown ZnO films were investigated systematically as a function of deposition temperature and growth time. Near-band edge ultraviolet (UV) emission was observed in room temperature photoluminescence spectra for the optimized samples, yet the usually observed defect related deep level emissions were nearly undetectable, indicating that high optical quality ZnO thin films could be achieved via this ultrasonic spray pyrolysis method. Considering the features of transferable and low thermal resistance of the graphite substrates, the achievement will be of special interest for the development of high-power semiconductor devices with sufficient power durability.

Electrophoretic deposition of polypyrrole/Vulcan XC-72 corrosion protection coatings on SS-304 bipolar plates by asymmetric alternating current for PEM fuel cells

In this study, corrosion protection composite films composed of polypyrrole (formed from the electropolymerization of pyrrol monomer) and Vulcan XC-72, labeled as PPy-C, were deposited on SS-304 substrates by EPD using an asymmetric AC signal (AAC) in acetone and acetone:methanol solutions. Prior to deposition, Vulcan powders were functionalized in order to create functional groups that develop a negative surface charge. Under the applied electric field, both pyrrole monomer and carbon colloidal particles migrated simultaneously toward the SS anode surface to create the corrosion protection PPy-C coatings. The effect of applied voltages (50, 70, 90 and 120 V) and deposition time (2, 6, 10 and 15 min) on the film characteristics was evaluated. The coatings were analyzed by SEM and the results showed improved characteristics of the films deposited by AAC, in terms of homogeneity and porosity, compared to samples prepared by a continuous DC process. Polarization curves were conducted in order to evaluate the corrosion characteristics of the bipolar plates in 0.1 M H2SO4 at room temperature. The experimental results indicated that the PPy-C composites significantly enhanced the corrosion resistance of the SS substrates. For example, the T1 sample increased the corrosion potential by about 541 mV and decreased the corrosion current density by two orders of magnitude, compared to uncoated SS. FTIR studies confirmed the formation of PPy after electropolymerization of the pyrrole monomer under the EPD process. Even though this characterization has been carried out in a half cell, it has been proposed that the PPy-C-coated SS bipolar plates may find application in the acidic atmosphere of PEMFCs.

Folates provoke cellular efflux and drug resistance of substrates of the multidrug resistance protein 1 (MRP1)

Cellular folate concentration was earlier reported to be a critical factor in the activity and expression of the multidrug resistance protein MRP1 (ABCC1). Since MRP1 mediates resistance to a variety of therapeutic drugs, we investigated whether the cellular folate concentration influences the MRP1-mediated cellular resistance against drugs. As a model system, we used the human ovarian carcinoma cell line 2008wt, and its stably MRP1/ABCC1-transfected subline 2008/MRP1. These cell types have a moderate and high expression of MRP1, respectively. In folate-deprived 2008/MRP1 cells, the MRP1-mediated efflux of its model substrate calcein decreased to ~55 % of the initial efflux rate under folate-rich conditions. In 2008wt cells, only a small decrease in efflux was observed. Folate depletion for 5-10 days markedly increased (~500 %) cellular steady-state accumulation of calcein in 2008/MRP1 cells and moderately in 2008wt cells. A subsequent short (24 h) exposure to 2.3 μM L-leucovorin decreased calcein levels again in MRP1-overexpressing cells. Folate deprivation markedly increased growth inhibitory effects of the established MRP1 substrates daunorubicin (~twofold), doxorubicin (~fivefold), and methotrexate (~83-fold) in MRP1-overexpressing cells, proportional to MRP1 expression. In conclusion, this study demonstrates that increased cellular folate concentrations induce MRP1/ABCC1-related drug efflux and drug resistance. These results have important implications in the understanding of the role of MRP1 and its homologs in clinical drug resistance.

Corrosion Behavior of Stainless Steel 304, Titanium, Nickel and Aluminium in Non-Aqueous Electrolytes

The corrosion behavior of stainless steel 304 (SS 304), titanium, nickel and aluminium is studied by immersion and anodic polarization tests in non-aqueous electrolytes. Tetraethyl ammonium tetrafluoroborate is used as a supporting electrolyte in the three kinds of solvents. The immersion test shows that chemical corrosion rate in propylene carbonate-based electrolyte is lower than those in acetonitrile- or <TEX>${\gamma}$</TEX>-butyrolactone-based electrolytes. Surface analyses do not reveal any corrosion product formed after the immersion test. In the anodic polarization tests, a higher concentration of supporting electrolyte gives a higher current density. In addition, a higher temperature increases the current density in the active region and reduces the potential range in the passive region. SS 304 shows the highest corrosion potential while Al shows the lowest corrosion potential and the highest current density in all studied conditions. Based on the conducted corrosion tests, the corrosion resistance of metal substrates in the organic solvents can be sorted in descending order as follows: SS 304 - Ti - Ni - Al.

TiO2/SiO2박막 코팅에 의한 폴리카보네이트 특성 개선

The property improvement of polycarbonate coated with a multilayer film composed of an inorganic film and a photocatalytic film was studied. The film as a binder had an excellent light transmission characteristic. After the treatment with atmospheric pressure plasma, the surface of film showed the hydrophilicity, which increased the film coating uniformity with a -containing aqueous solution. When film was over 200 nm thick, the absorption effect of UV rays in the range of 180~400 nm suppressed the yellowing phenomena of polycarbonate substrate. The inorganic film improved the heat resistance of polycarbonate substrates. film in the outmost under the exposure of UV rays promotes the catalytic oxidation characteristics and yields the capability to the decomposition of organic contaminants, and also increases the self-cleaning properties due to the increase of hydrophilicity. Structural stability of the polycarbonate substrate coated with inorganic and film was shown. The role of film between and polycarbonate substrate suppressed the peeling of film by inhibiting the photocatalytic oxidation effect of film on the polycarbonate substrate.

Ceramic Alumina Substrates for High-temperature Gas Sensors – Implications for Applicability

In the field of gas sensors and high temperature flow sensors, thick-film based structures play a key role, particularly in harsh environments. Their substrates have to be electrically insulating and chemically inert. Alumina substrates are often considered as ideal sensor substrates. However, neither their electrical resistivity nor their chemical inertness is ideal. Even the thermal conductivity is that temperature dependent that one has to consider it when modeling temperature profiles. Measurements on the resistivity and the thermal conductivity between room temperature and 800oC of alumina substrates are presented in this contribution together with data how the resistance of naked alumina substrates is affected by NO2.

Effect of Thermal-Sprayed Mn1.5Co1.5O4 Coating on Oxidation Suppression of Metallic Interconnects

Metallic interconnects are less expensive, more conductive and able to form complex shapes than ceramic interconnects for SOFC applications. Most metallic interconnects use alloys containing chromium. At elevated temperatures, chromia scales react with cathode and degrade its performance. Manganese cobalt oxide ((Mn,Co)3O4 , (MCO), with spinel structure is found to be a good material to form a protective coating for metallic interconnects. In this study, the high-temperature ferritic stainless steel Crofer 22H and nickel-chromium alloy Inconel 625 were thermally sprayed with MCO, and the oxidation, scale structure, and resistance of metallic substrates were investigated using XRD, TEM and SEM.

Microstructure and Wear Resistance of Laser Clad Fe-Cr3C2 Composite Coating on 35CrMo Steel

Fe-Cr3C2 hard coatings with varying Cr3C2 content were produced on 35CrMo steel substrates by laser cladding. The experimental results showed that the coatings were uniform, continuous, and free of cracks. High adhesions between all produced coatings and their corresponding substrates were obtained due to the metallurgical interfaces between them. The microstructures of the coatings were mainly composed of austenitic dendrites and M7C3. The microhardness gradually increased from the bottom to the top of the coating, and increased with elevation of Cr3C2 content. The Fe-Cr3C2 coatings improved the sliding wear resistance of the 35CrMo steel substrates obviously, and the dominant wear mechanism was spalling fatigue, with plowed grooves on the worn surfaces.

Increasing the Corrosion Resistance of Mullite-based Catalyst Substrates in a Vehicle Exhaust Environment

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Optimization of 316L stainless steel coatings on light alloys using Cold Gas Spray

Spherical 316L stainless steel powder was deposited onto light alloys by Cold Gas Spray (CGS). The main objective was to obtain thick coatings and thus improve the wear resistance of the light alloy substrates while maintaining the high oxidation resistance that characterizes 316L stainless steel. To optimize the coatings, the pressure and temperature of the streaming gas were varied in an experimental design matrix. The physico-chemical properties and deposition efficiency of cold-sprayed 316L stainless steel coatings were studied. Deposition efficiency, porosity and wear resistance properties of the coatings were analyzed. The coatings achieved under the highest pressure and temperature+ were denser, thicker and with a higher wear resistance than those obtained under lower energy. The hardness and wear resistance of the light alloy substrate were improved over those obtained by conventional spraying techniques.

Characteristic Corrosion Resistance of Nanocrystalline TiN Films Prepared by High Density Plasma Reactive Magnetron Sputtering

Nanocytalline TiN films were deposited on non-alkali glass and Al substrates by reactive DC magnetron sputtering (DCMS) with an electromagnetic field system (EMF). The microstructure and corrosion resistance of the TiN-coated Al substrates were estimated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. All the TiN films shows that they have a (111) preferred orientation at room temperature. TiN films deposited on Al substrate using only DCMS 400 W showed a sheet resistance of 3.22 x 10-1 omega/symbol see texts (resistivity, 3.22 x 10-5 omegacm). On the other hand, a relatively low sheet resistance of 1.91 x 10-1 omega/symbol see text (1.91 x 10-5 omegacm) was obtained for the dense nanocrystalline TiN film deposited on Al substrate using DCMS 375 W+ EMF 25 W, indicating that the introduction of an EMF system enhanced the electrical properties of the TiN film. TiN films deposited on Al substrate at 400 degreesC had a (200) preferred orientation with the lowest sheet resistance of 1.28x10-1 omega/symbol see texts (1.28 x 10-5 omegacm) which was attributed to reduced nano size defects and an improvement of the crystallinity. Potentiostatic and Potentiodynamic tests with a TiN-coated Al showed good corrosion resistance (l/corr, = 2.03 microA/cm2, Ecorr = -348 mV) compared to the uncoated Al substrate (/corr = 4.45 microA/cm2, Ecorr = -650 mV). Furthermore, EMF system showed that corrosion resistance of the TiN film also was enhanced compared to DCMS only. For the TiN film deposited on Al substrate at 400 degreesC, corrosion current and potential was 0.63 micro/cm2 and -1.5 mV, respectively. This improved corrosion resistance of the TiN film could be attributed to the densification of the film caused by enhancement of nitrification with increasing high reactive nitrogen radicals.

Double layer bioglass-silica coatings on 316L stainless steel by sol–gel method

Abstract The application of bioglass coatings on metallic implants provides link between bone and materials and prevents corrosion of metallic implants in body fluid. Therefore, in this research, 45S5 bioglass-silica coatings on 316L stainless steel were prepared by the sol–gel method and were characterized by different techniques. According to X-ray diffraction (XRD) results, by sintering 45S5 bioglass at 600 °C for 5 h, coatings containing both amorphous phase and Na2Ca2Si3O9 crystalline phase were obtained. Scanning electron microscopy (SEM) results showed that coatings prepared via appropriate sol aging and substrate preparations are crack-free. Potentiodynamic polarization tests in simulated body fluid (SBF) showed that coatings improve corrosion resistance of substrates, significantly. Further, bioactivity was considered during 30 days of immersion in SBF at 37 °C by atomic absorption spectroscopy (AAS), XRD, SEM and potentiodynamic polarization tests that demonstrated the growth of amorphous apatite, hydroxyapatite (HA) and CaSiO3 film on coatings.

Effect of ceramics coating using sol–gel processing on corrosion resistance and age hardening of AZ80 magnesium alloy substrate

Extruded plates of AZ80 magnesium alloy were coated with CeO2 and/or MgO ceramics by sol–gel processing. We investigated the effects of heat treatment conditions, under which the ceramic thin film was formed, on the mechanical properties and corrosion resistance of the substrates. Single layer (CeO2 or MgO) and double layer (CeO2/MgO) ceramic thin films were successfully formed from precursor solution by the sol–gel processing under optimal heat treatment, in which the AZ80 original substrates were age-hardened. The corrosion resistance of AZ80 magnesium alloy substrates evaluated by the salt water immersion test was found to be improved by ceramic coating and microstructural change of the original substrate during coating process. The double layer ceramic coating was superior to the single layer coatings in terms of corrosion resistance. The acquisition of corrosion resistance in AZ80 magnesium alloy substrates could be applied simultaneously by sol–gel processing, while the substrates were age-hardened by the heat treatment.

Factors influencing the ballistic impact resistance of elastomer-coated metal substrates

An experimental study was carried out of various factors affecting the ballistic penetration resistance of elastomer/steel bilayers. For blunt penetrators, the contribution of the coating to performance is optimized using the hardest substrates, front surface placement of the elastomer, and (when normalizing by added weight) thin, ca. 2–3 mm, coatings. These results, none of which are predicted by existing models, evince the marked coupling of coating and substrate in the impact response of the bilayer. We also show that nanoparticle fillers have a modest effect on ballistic performance of polyurea coatings, changing the penetration velocity by a few percent or less. This contrasts with the linear dynamic mechanical behavior, which shows much more significant increases in energy absorption due to nano-reinforcement.

The function of ABCB transporters in auxin transport

Plant ATP-binding cassette (ABC) transporters consist of largest family members among many other membrane transporters and have been implicated in various functions such as detoxification, disease resistance and transport of diverse substrates. Of the ABC-B/multi-drug resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily, at least five members have been reported to mediate cellular transport of auxin or auxin derivatives. Although single mutant phenotypes of these genes are milder than PIN-FORMED (PIN) mutants, those ABCBs significantly contribute for the directional auxin movement in the tissue-level auxin-transporting assay. Uniformly localized ABCB proteins in the plasma membrane (PM) are generaly found in different plant species and stably retained regardless of internal and external signals. This implies that these ABCB proteins may play as basal auxin transporters.

Elaboration and Characterization of Siloxane-PMMA Hybrid Films on Tinplate Substrates

The characteristics of siloxane-PMMA hybrid films permit the obtaining of coatings with thickness of few microns without cracking. Besides, the methacrylate groups (MMA) can be easily polymerizated by UV irradiation or thermal treatments. These hybrids can also be applied in anti-corrosive coatings for metals and alloys, replacing chromates which exhibit high toxicity. In this context, the aim of this work is to study the behavior of tinplate coated with a siloxane-PMMA hybrid film by dip-coating process and cured by thermal cure process. The systems were characterized by electrochemical, morphological and physicochemical analysis. Preliminary results showed that the systems studied presented a regular and adherent siloxane-PMMA hybrid film, which increased the corrosion resistance of tinplate substrates.

Studies on palladium coated titanium foams cathode for Mg–H2O2 fuel cells

The corrosion resistance of several cathode substrates (titanium foam, nickel foam, and silver coated nickel foam) of magnesium–hydrogen peroxide (Mg–H2O2) fuel cells is studied. Titanium foam is found to be the most corrosion-resistant, i.e., the corrosion current density of titanium foam is six orders of magnitude lower than that of nickel or Ag–Ni. Palladium catalyzed titanium foam as a cathode for the Mg–H2O2 fuel cell is prepared by electrodepositing palladium onto the titanium foam substrate. The corrosion resistance of prepared palladium coated titanium is compared with that of titanium foam, nickel foam, and silver coated nickel foam. The structure, morphology and composition of the Pd/Ti are characterized by SEM, EDS, XRD techniques. The influence of the concentration of hydrogen peroxide, sulfuric acid and operation temperature on the performance of Mg–H2O2 fuel cells with the Pd/Ti cathode is studied systematically. The stability of the Mg–H2O2 fuel cell with the Pd/Ti as the cathode is tested and the result shows that Pd/Ti is a promising cathode material for Mg–H2O2 fuel cells.

Electrochemical deposition of barium titanate thin films on TiN/Si substrates

Barium titanate (BaTiO3) films were synthesized on TiN-coated Si substrates by electrochemically anodic oxidation in mixed alkaline electrolytes of 0.5M Ba(CH3COO)2 and 2M NaOH. A potentiostatic mode was conducted to make the films with the voltages ranging from 2 to 60V at 70°C for only 1min. X-ray diffraction results show that cubic BaTiO3 films were successfully prepared on TiN-coated substrates at the reaction voltages above 2V. Field-emission scanning electron microscopy revealed that the obtained BaTiO3 films possessed uniformly distributed spherical-particulate surface morphology with a nanolayered feature. The thickness of BaTiO3 could reach about 4μm after electrochemical oxidation with the voltage of 60V. The growth rate of BaTiO3 films synthesized by the electrochemical oxidation was much faster than that of the films prepared by the previously reported hydrothermal and hydrothermal–galvanic couple methods where only a single layer was produced. Potentiodynamic polarization reveals that the corrosion resistance of TiN-coated substrates was greatly improved by electrochemical deposition of the dense and thick BaTiO3 films over the substrates.

AN INVESTIGATION ON EFFECTS OF TiO2 NANO-PARTICLES INCORPORATED IN ELECTROLESS NiP COATINGS' PROPERTIES

Electroless composite coatings have been vastly used in various industries during last decades due to their good properties, such as corrosion and wear resistance, hardness and uniform thickness. In this paper, co-deposition of TiO 2 nano-particles with Nickel-Phosphorus electroless coatings on API-5L-X65 steel substrates was investigated. Surface morphology and composition of coatings were studied via SEM and EDX, respectively. XRD analyses showed that these coatings had amorphous structure with TiO 2 crystalline particles. TiO 2 nano-particles increased microhardness of coatings. Corrosion resistance of these coatings was tested using linear polarization in 0.5M sulfuric acid electrolyte. Results showed that NiP - TiO 2 electroless composite coatings increased corrosion resistance of substrates.

Evaluation of the effect of deposition bath glycerol content on zinc–nickel electrodeposits on carbon steel

Zn–Ni electrodeposits have been used to improve the corrosion resistance of carbon steel substrates in several applications, mainly in the aeronautical, oil, gas, and automotive industries. The use of component compounds that increase deposition efficiency and corrosion resistance has attracted growing interest. In this study, the effect of glycerol bath content (to a concentration of 0.34mol/L) in bath deposition was analyzed. The deposition efficiency was analyzed by galvanostatic and potentiodynamic deposition, and the corrosion resistance was estimated with electrochemical tests, and mass loss measurements. The deposits were characterized by X-ray fluorescence, X-ray diffraction, and scanning electron microscope. The results indicate that there is a significant increase in the deposition efficiency and corrosion resistance when using glycerol concentrations up to 0.07mol/L. For glycerol concentrations between 0.14 and 0.34mol/L, there is a decrease in the deposition efficiency, and these concentrations do not result in a clear increase in the corrosion resistance of the Zn–Ni deposit. Analysis of the effect of deposition bath glycerol on the deposition efficiency and corrosion resistance of a Zn–Ni alloy indicates that this effect is related to the morphology of the deposit. The addition of glycerol to the deposition bath solution deposition results in grain refinement and the formation of a more compact deposit.