Physical Barrier Layer Research Articles

High corrosion-resistant octanoic acid vapor-phase modified Ce-LDH surface film of aluminum alloy

The cerium salt modified LDH coating (Ce-LDH coating) was produced on AA5052 Al alloy surface by in-situ hydrothermal synthesis. The vapor phase assembly of octanoic acid (OA) was adopted to improve the further hydrophobicity of Ce-LDH layer. The octanoic acid modified Ce-LDH coating (VOA-Ce-LDH coating) was successfully prepared on AA5052 Al alloy. It indicates that the VOA-Ce-LDH coating has excellent anti-corrosion protection with a protection efficiency of 96.95%. VOA-Ce-LDH coating contains two different layers. The outer layer is an octanoic acid (OA) vapor phase assembly layer and a Zn-Al LDH layer. The inner layer is Al(OH)3 (aluminum hydroxide) layer. The physical barrier layer of OA and the corrosion ion trapping function of LDH give the good anti-corrosion protection of the modified coating. This study is helpful for the development of vapor phase corrosion inhibitors and LDH coating for corrosion protection on metal materials.

Preparation of new surface coating based on modified oil-based polymers blended with ZnO and CuZnO NPs for steel protection

In our paper, we have synthesized modified PEA and alkyd resin by replacing the new source of polyol (SDEA) which was confirmed by different analyses such as IR, and 1HNMR spectra. A series of conformal, novel, low-cost, and eco-friendly hyperbranched modified alkyd and PEA resins were fabricated with bio ZnO, CuO/ZnO) NPs through an ex-situ method for mechanical and anticorrosive coatings. The synthesized biometal oxides NPs and its composite modified alkyd and PEA were confirmed by FTIR, SEM with EDEX, TEM, and TGA, and can be stably dispersed into modified alkyd and PEA resins at a low weight fraction of 1%. The nanocomposite coating was also subjected to various tests to determine their surface adhesion, which ranged from (4B-5B), physico-mechanical characteristics such as scratch hardness, which improved from < 1.5 to > 2 kg, gloss (100–135) Specific gravity (0.92–0.96) and also chemical resistance test which passed for water, acid, and solvent except alkali, was poor because of the hydrolyzable ester group in the alkyd and PEA resins. The anti-corrosive features of the nanocomposites were investigated through salt spray tests in 5 wt % NaCl. The results indicate that well-dispersed bio ZnO and CuO/ZnO) NPs (1.0%) in the interior of the hyperbranched alkyd and PEA matrix improve the durability and anticorrosive attributes of the composites, such as degree of rusting, which ranged from 5 to 9, blistering size ranged from 6 to 9, and finally, scribe failure, which ranged from 6 to 9 mm. Thus, they exhibit potential applications in eco- friendly surface coatings. The anticorrosion mechanisms of the nanocomposite alkyd and PEA coating were attributed to the synergistic effect of bio ZnO and (CuO/ZnO) NPs and the prepared modified resins are highly rich in nitrogen elements, which might be regarded as a physical barrier layer for steel substrates.

An ultra-thin inorganic interlayer strategy for achieving efficient inverted planar perovskite solar cells and modules with high fill factor

The fill factor (FF) is a fatal parameter to determine the power conversion efficiency (PCE) of perovskite solar cells. Especially, for the large area solar cells and modules, the low FF is the bottleneck towards the high PCE. The FF is highly correlated with the carrier recombination caused by defects at interfaces. Herein, we propose that ultra-thin inorganic alkali metal fluorides interlayer passivate the interface defects by vapor evaporation method at the perovskite/electron transport layer (ETL) interface. We confirmed that the alkali metal fluorides (AF) layer can function as both defect passivation layer and physical barrier layer, showing the significant enhancement of PCE and ambient stability. Eventually, we achieve the highest FF (80.6%) for 1 cm 2 size and highest FF (73.1%) for 10.8 cm 2 size perovskite solar cell by potassium fluoride (KF) as passivation layer. This functional interlayer strategy paves the way to resolve the industrial requirements with low cost, high fill factor large area planar perovskite solar cells. • As for the alkali metal fluorides as passivation layer, the introduce of alkali metal fluorides can effectively reduce the defects at the perovskite surface: the alkali metal fluorides can improve fluorescence intensity and fluorescence lifetime, so that to decrease the surface defect evoked by the surface vacancy. • As for the alkali metal fluorides as physical barrier layer, the introduce of alkali metal fluorides can effectively reduce the carrier recombination at perovskite/transport layer interfaces and improve ambient stability: The inserted inorganic layer can selectively conduct one type of charges while block the other type, which spatially separates photogenerated electrons and holes to reduce their recombination • The inserted inorganic layer increases the contact angle, which obviously improves the device stability.

Thermal decomposed behavior and kinetic study for untreated and flame retardant treated regenerated cellulose fibers using thermogravimetric analysis

In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame retardants. Limited oxygen index and microscale combustion calorimeter tests show that the loading of nitrogen/silicon into the RCF enhanced flame retardancy. The kinetic triplets of the two kinds of samples were determined by applying iso-conversional methods and integral master plots approach. Compared to the untreated RCF, flame retardant (FR) treated RCF shows enhanced activation energy due to the physical barrier layer due to dehydration of silicate and charring effect resulting from organic–inorganic interaction. Exponential nucleation model can be successful in describing experimental results for RCF in higher conversion degree (0.4–0.9). Simultaneously, the degradation process of FR treated RCF in the main pyrolysis stage (0.2–0.7) is consistent with kinetics of nuclei growth and could be described by one-step reaction whose rate presented an Avrami–Erofeev-type model (n = 2.38).

Characterization of Gel Polymer Electrolytes Based on Poly (Ionic Liquid)-Glyme Mixtures for Lithium Metal Batteries

Solid polymer electrolytes (SPE) have generated an extensive and sustained interest for its application in lithium metal batteries.[ 1 ] Compared with liquid electrolytes, solid polymer electrolytes have higher safety and thermal stability, since they can provide a physical barrier layer to prevent efficiently lithium dendrite growth and avoid thermal runaway under high temperature or impact. Despite the substantial benefits, some limitations remain to be improved, such as a low ionic conductivity at room temperature and low transference number. Several studies are being conducted to overcome these weaknesses and develop new generation of solid polymer electrolyte lithium metal batteries.[ 2 ] Most of the research on SPEs is focused on polyethylene oxide (PEO) mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and its derivative. In general, PEO-based solid electrolytes have shown good dimensional stability, good safety, and can mechanically prevent dendritic growth. However, they exhibit low ionic conductivity and rather low cationic transference number (t+) of ca. 0.15. To achieve sufficient conductivity at low temperatures, polymers that are difficult to crystallize are proposed. Ionic liquids (IL) are poor crystal formers; therefore, polymers of IL are potentially good alternatives to PEO for lower temperature conductivity. An Iongel membrane based on the poly(dimethyldiallylammonium) polyDADMA-TFSI poly(ionic liquid) has gained attention in polymer metal batteries due to its favorable mechanical properties and stability against Li-metal.[ 3 ] The present study provides an insight into the properties of free-standing membranes using poly (ionic liquid)-glyme mixtures compared to typical polymer salt blends (PEO-LiTFSI) and PDADMA-LiTFSI. The benefit of tetraethylene glycol dimethyl ether (G4) is highlighted and appears to be the key component to obtain higher ionic conductivity regardless on the type of polymer used. The impact of the increase in LiG4TFSI/poly ionic liquid ratio within the electrolyte on the transference number, ionic conductivity and mechanical properties was further analyzed. For 33-66 wt% composition for PDADMAT-LiG4TFSI and PEO-LiG4TFSI membranes, a good compromise between the physicochemical and electrochemical properties was achieved.

Effects of hyperbranched polyesters covalent functionalized multi-walled carbon nanotubes on the mechanical and tribological properties of epoxy composites

In order to improve the mechanical and tribological properties of epoxy composites, the hyperbranched polyesters with terminal carboxyl (HBP) were used for covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The dispersibility and wettability of functionalized MWCNTs (HBP-NH2-MWCNTs) in epoxy resin (EP) were analyzed. The HBP-NH2-MWCNTs reinforced EP composites (HBP-NH2-MWCNTs/EP) were prepared. The microhardness and fracture toughness of HBP-NH2-MWCNTs/EP were tested, and the tribological behavior and mechanism under dry friction conditions were investigated. The results show that the hyperbranched polyesters coated on the surface of MWCNTs forms a physical barrier layer, blocking the van der Waals force between MWCNTs, effectively reducing the agglomeration phenomenon and significantly improving its dispersibility and wettability. Meanwhile, The flexible hyperbranched polyester on the surface of MWCNTs alleviates the stress concentration of the interface and improves the load transfer efficiency, which greatly improves the microhardness and fracture toughness. Under dry friction conditions, the friction coefficient and wear loss of HBP-NH2-MWCNTs/EP composites showed a trend of decreasing first and then increasing as the content of HBP-NH2-MWCNTs increased from 0.3 phr to 1.2 phr. When the content of HBP-NH2-MWCNT is 0.6 phr, the composites has the lowest friction coefficient and the wear loss, and the wear mechanism is mainly characterized by slight fatigue wear.

Investigation on the flow-induced corrosion and degradation behavior of underground J55 pipe in a water production well in the Athabasca oil sands reservoir

The corrosion behavior of J55 carbon steel pipe was investigated in a water production well environment in the Athabasca oil sands reservoir. The corrosion morphologies and the chemical compositions of corrosion products were examined by surface analysis techniques. The protection performance of the formed corrosion scales was evaluated using electrochemical measurements. The results show that severe erosion corrosion occurs on the inner wall of the pipe and causes a significant thinning, which is the dominant reason for the pipe failure. Likewise, the failure of the thread zone is originated from the severe corrosion of inner wall as well. Localized corrosion of carbon steel occurs in the welding zone because of the galvanic effect between stainless steel and carbon steel. Furthermore, the distributions of corrosion products on the inner wall are notably affected by the flow. Dense and thick Ca-containing corrosion scales act as a physical barrier layer and prevent the steel from further corrosion, whereas localized corrosion occurs in the regions with loose and thin corrosion scales.

Enhanced in Vitro and in Vivo Performance of Mg-Zn-Y-Nd Alloy Achieved with APTES Pretreatment for Drug-Eluting Vascular Stent Application.

Bioabsorbable magnesium alloys are becoming prominent as temporary functional implants, as they avoid the risks generated by permanent metallic implants such as persistent inflammation and late restenosis. Nevertheless, the overfast corrosion of Mg alloys under physiological conditions hinders their wider application as medical implant materials. Here we investigate a simple one-step process to introduce a cross-linked 3-amino-propyltrimethoxysilane (APTES) silane physical barrier layer on the surface of Mg-Zn-Y-Nd alloys prior to electrostatic spraying with rapamycin-eluting poly(lactic-co-glycolic acid) (PLGA) layer. Surface microstructure was characterized by scanning electron microscope and Fourier transform infrared spectroscopy. Nanoscratch test verified the superior adhesion strength of PLGA coating in the group pretreated with APTES. Electrochemical tests combined with long-term immersion results suggested that the preferable in vitro anticorrosion behavior could be achieved by dense APTES barrier. Cell morphology and proliferation data demonstrated that APTES pretreated group resulted in remarkably preferable compatibility for both human umbilical vein endothelial cells and vascular smooth muscle cells. On the basis of excellent in vitro mechenical property, the animal study on the APTES pretreated Mg-Zn-Y-Nd stent implanted into porcine coronary arteries confirmed benign tissue compatibility as well as re-endothelialization without thrombogenesis or in-stent restenosis at six-month followup.

Enhanced corrosion resistance and biocompatibility of Mg-Zn-Y-Nd alloy achieved with APTES pre-treatment for drug-eluting vascular stent application

Event Abstract Back to Event Enhanced corrosion resistance and biocompatibility of Mg−Zn−Y−Nd alloy achieved with APTES pre-treatment for drug-eluting vascular stent application Jing Liu1, Tingfei Xi1 and Ming Chen2 1 Peking University, Academy for Advanced Interdisciplinary Studies, China 2 Peking University First Hospital, Cardiovascular Internal Medicine Department, China Bioabsorbable magnesium alloys (Mg) are advantageous in temporary functional implant applications, as they avoid the risks posed by permanent metallic implants. Nevertheless, the over-fast corrosion of Mg alloys under physiological conditions hinders its wider use as medical implants. Here we introduce a convenient one-step process to introduce a cross-linked 3-amino-propyltrimethoxysilane (APTES) silane physical barrier layer on the surface of Mg-Zn-Y-Nd alloys before coating with drug-eluting poly (glycolide-co-lactide) (PLGA) layer loaded with rapamycin. Surface microstructure was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). Nano-scratch test verifies the adhesion strength of the PLGA pre-treated with APTES is superior to direct PLGA coating. Electrochemical testing combined with long-term immersion results indicate that the APTES coating results in preferable in vitro anti-corrosion behaviour. Cell morphology and proliferation tests demonstrate that APTES pre-treated Mg-Zn-Y-Nd substrate shows markedly preferable effects for both human umbilical vein endothelial cells (EA. hy926) and vascular smooth muscle cells (VSMC). Furthermore, the in vivo test via implanting APTES pre-treated Mg-Zn-Y-Nd stent to porcine coronary arteries for 6 months confirms benign tissue compatibility with the well re-endothelialized vessel with no sign of obvious thrombogenesis and restenosis. National Basic Research Program of China (Grant No. 2012CB619102); Shenzhen Science and Technology Funding Projects (CXZZ20140730091722497); Shenzhen Special Funds for Development of Strategic Emerging Industries(Project No. JCYJ20130402172)

The effect of TiO 2 as a pigment in a polyurethane/polysiloxane hybrid coating/aluminum interface based on damage evolution

Abstract The effect of titanium oxide as an additive on the performance of a polyurethane/polysiloxane hybrid coating was characterized by an electrochemical approach. The performance evolution was quantified by exposing the hybrid coating on an aluminum substrate to NaCl solution at pH 5 over time. Real-time measurements were performed to quantify and correlate the mechanisms that occur at the coating/substrate interface. Electrochemical impedance spectroscopy (EIS) quantified the hybrid coating/substrate interface performance over the course of the 263 days of exposure, and electrically passive elements described and characterized the degradation/performance stages upon exposure to the acidic NaCl solution. The addition of TiO2 produced hydrophobicity functionality, and TiO2 acted as a physical barrier layer that influenced the initial damage stage. Different exposure times were associated the different stages of damage evolution for the hybrid coating and coating/substrate interfaces. Electrochemical testing with high-resolution techniques such as AFM (atomic force microscope) and IFM (infinite focus microscope) characterized the coating surface and the interface performance and resolved the surface and defect formation observed with different levels of TiO2 content. Of the systems tested, the system with 10 wt% TiO2 provided the best corrosion inhibition.

Effect of Pd Interlayer on Electrochemical Properties of ENIG Surface Finish in 3.5 wt.% NaCl Solution

The corrosion resistance of a multilayered (NiP-Pd-Au) coating with various thicknesses of palladium (Pd) interlayer deposited on copper by an electroless method was investigated using electrochemical techniques including potentiodynamic polarization and electrochemical impedance spectroscopy. In addition, the surface finish was examined by x-ray diffraction analysis and scanning electron microscopy, and the contact angle of the liquid–solid interface was recorded. The corrosion resistance of the copper substrate was considerably improved by Pd interlayer addition. Increase of the thickness of the Pd interlayer enhanced the performance of the Cu-NiP-Pd-Au coating due to low porosity, high protective efficiency, high charge-transfer resistance, and contact angle. These are attributed to the diffusion of layers in the Cu-NiP-Pd-Au coating acting as a physical barrier layer, leading to the protection provided by the coating.

Surface modification of PDMS by atmospheric-pressure plasma-enhanced chemical vapor deposition and analysis of long-lasting surface hydrophilicity

Atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) offers several benefits such as simplicity, high productivity, and versatility. An AP-PECVD-based method is proposed in this study to modify hydrophobic PDMS (polydimethylsiloxane) surfaces towards a long-lasting hydrophilic character. To enhance the sustainability of the hydrophilicity, two kinds of layers were sequentially deposited by AP-PECVD on the surface of a PDMS block (TEOS-O2/CH4/PDMS). A hydrocarbon layer was first coated on the bare PDMS surface using CH4 as the reactant, and then, a hydrophilic SiOx layer was deposited using tetraethyl orthosilicate and oxygen (TEOS-O2). The highly cross-linked hydrocarbon layer acted as a physical barrier layer (PBL) between the bare PDMS surface and the hydrophilic layer. To confirm that the PBL suppresses the hydrophobic recovery of the modified PDMS surface with double layer, a single-layer-coated PDMS sample (TEOS-O2/PDMS) without the PBL was prepared by AP-PECVD using TEOS-O2. The surface characteristics were determined by static contact angle measurements, surface roughness measurements, and surface chemical composition/chemical bonding determination and compared with those of modified PDMS surface with double layer. The surface morphology of TEOS-O2/PDMS degraded seriously by the diffusion of PDMS oligomers to the hydrophilic layer, but that of TEOS-O2/CH4/PDMS was sustained for a long time. Thus, TEOS-O2/CH4/PDMS had the lowest contact angle, almost 0°, and showed long-lasting surface hydrophilicity, with almost no change in the contact angle for 28 days. Thus, this proposed method is confirmed to be well suited for use in applications that require stable hydrophilic surface property in PDMS.

Effect of thermal treatment on the corrosion resistance of polyaniline in H 2SO 4–HF acid mixture solution

The corrosion resistance and conduction properties of polyaniline (PANi)-coated 316L stainless steel were improved by the thermal treatment. Electrochemical analyses of the PANi specimens demonstrated excellent corrosion resistance with high protection efficiency (⩾96.21%) and charge transfer resistance, as well as a very low corrosion current density (<1 μA/cm 2). In addition, it also performed better conductive properties due to lower contact and surface resistance (<5 Ω cm 2), comparing with untreated specimens. These were attributed to the presence of the interaction of the carbonyl group with the NH group in PANi as a physical barrier layer, which provides passivity protection in polymer coatings.

Charge relaxation and instability in barrier layers

It is shown experimentally that the order of magnitude of the relaxation time of a physical barrier layer is determined by the product of the Maxwell relaxation time and the corresponding exponent. The experiments deal with dielectric dispersion in ferrites and nickel oxide. It is shown that near the relaxation maximum these inhomogeneous semiconductors can be considered as quasihomogeneous. A new treatment of a number of instabilities in barrier layers is presented: low frequency voltage fluctuations in p—n junctions and Schottky barriers, barrier instability, etc.