IR Drop Research Articles

Making use of external corrosion defect assessment (ECDA) data to predict DCVG %IR drop and coating defect area

Buried pipelines are vulnerable to the threat of corrosion. Hence these pipelines are coated with a protective layer (coating) to isolate the metal substrate from the surrounding environment. With time, the coating will deteriorate which could lead to corrosion. The condition of the coating can be investigated by the external corrosion direct assessment (ECDA) procedure to investigate and monitor corrosion activity on unpiggable pipelines and provides a guideline in maintaining its structural integrity. This paper highlights the results obtained from the ECDA process which was conducted on 250 km of buried pipelines. The results from the indirect and direct assessment part of the ECDA were modeled using the classical quantile regression (QR) and the Bayesian quantile regression (BQR) method to investigate the effect of factors toward the IR drop (%IR) and the coating defect size (TCDA). It was found that the classical method and the Bayesian approach produces similar predictions on the regression coefficients. However, the Bayesian method has the added advantage of the posterior distribution which considers parameter uncertainties and can be incorporated in future ECDAs.

Crevice Corrosion Performance of 436 Ferritic Stainless Steel Studied by Different Electrochemical Techniques in Sodium Chloride Solutions with Sulfate Addition

The crevice corrosion behaviors of 436 stainless steels in chloride-containing solutions with sulfate addition were studied using potentiodynamic, galvanostatic and repassivation potential measurements. The results of these electrochemical tests were compared and discussed. Galvanostatic test was proved to be the most powerful technique in detecting the crevice corrosion of 436 stainless steels, while the repassivation potential measurement was the most time-saving method in this study. Sulfate ions have inhibited the crevice corrosion of 436 stainless steels in chloride-containing solution, which may result from the effects of competitive adsorption and the IR drop mechanism.

Electrochemical characteristics of flexible micro supercapacitors with reduced graphene oxide-carbon nanotubes composite electrodes

In this study, we fabricate solid-state flexible micro-supercapacitors (MSCs) with reduced graphene oxide-carbon nanotube (rGO-CNT) composite electrodes and investigate the electrochemical characteristics by comparing with those of an MSC with rGO electrodes. Regarding the resistance-capacitance time constant and IR drop, the addition of CNTs into the rGO electrodes shows a significant effect owing to both the decrease in the resistance and the increase in the permeability of the electrolytes. Compared to the rGO MSCs, the rGO-CNT MSCs show an excellent areal capacitance of 2.6 mF/cm2, a smaller IR drop of 11 mV, a lower RC time constant of 6 ms, and faster charging/discharging rates with a high scan rate ability up to 100 V/s. The mechanical stability of the flexible rGO-CNT MSCs is verified by 1000 bending cycles. In addition, the electrochemical characteristics of the flexible rGO-CNT MSCs are maintained regardless of the MSC array type.

Rational synthesis of porous carbon nanocages and their potential application in high rate supercapacitors

Exploration of carbon nanoarchitectures with lower cost and excellent rate capability is of great importance, however, still remains a significant challenge. In the present work, a facile procedure for the fabrication of porous carbon nanocages (PCNCs) with a superior rate capability for supercapacitors has been developed. This approach is based on directly carbonization of sodium polyacrylate and subsequently chemical etching through a simple immersing-filtration-activation process. The extraordinary structures and morphologies of PCNCs has lots of structural advantages for supercapacitor applications. The supercapacitor assembled with the optimized sample can deliver a large specific capacitance (161 F/g at 1 A/g), superior rate capability (capacitance retention as high as 77.6% at 30 A/g), tiny IR drop (0.407 V at 30 A/g). Furthermore, in view of the wide working voltage (2.7 V) and excellent rate capability, the energy densities can retain at 30.2 Wh/kg at a large power density of 20.3625 kW/kg. Remarkably, the as-assembled supercapacitor can light 11 red light-emitting diodes (LED, 1.5 V) in parallel highlighting its enormous potential for practical applications.

Tunable synthesis of nanocarbon architectures and their application in advanced symmetric supercapacitors

Controllable fabrication of carbonaceous materials has aroused considerable interest, however, the development of template-free methods for the synthesis of nanocarbons with tunable architectures still remains a significant challenge in both experimental design and theoretical research. Herein, this study demonstrates the straightforward process for the selectively production of porous carbons nanoarchitectures including porous carbon microfibers (CMFs), carbon nanosheets (CNs) and carbon nanosheets decorated with hollow sphere (CNDHS) via a novel KNO3 activation process with cotton as the precursor. We found that not only the morphologies, but also the specific surface area and the pore size distributions of the products are drastically associated with the concentration of KNO3. In particular, the unique 2D nanosheets decorated with hollow spheres endow the CNDHS with large specific surface area (2091 m2/g), narrow micropores (1.38 nm), small internal resistance (0.87 Ω), and low level of heteroatoms content. Benefiting from the synergistic effects of these intrinsic features, the symmetric supercapacitors based on CNDHS display outstanding electrochemical performance including high specific capacitance of 183 F/g at 1 A/g, excellent rate capability of 62.8% at 50 A/g, small IR drop (0.735 V at 50 A/g), good cycling stability (91.1% of capacitance retention after 10,000 cycles) in 1 M TEABF4/AN electrolyte. Moreover, the proper integrated large energy density (28.875 W h/kg) with high power density (37.125 kW/kg) demonstrated again that the present work may provide a new path for the design and production of various nanocarbon architectures for energy storage related applications.

Unusual carbon nanomesh constructed by interconnected carbon nanocages for ionic liquid-based supercapacitor with superior rate capability

The exploration of various porous nanocarbon materials with an extraordinary electrochemical capacitive performance in ionic liquid (IL) electrolytes is urgently needed for development of the next-generation energy storage devices. Significant improvements in energy density have been achieved, however, supercapacitors with IL electrolytes usually suffer from issues related to low power density and large IR drop. Herein, we report an unprecedented carbon nanomesh that is made up of interconnected densely-packed carbon nanocages with ultrathin partially graphitic shells. The large specific surface area and well-developed mesopores combined with its unique structural features, make it a very competitive material for high-performance supercapacitor in IL electrolyte. Notably, this unique nanosheets morphology with lots of in-plane nanopores on their surface can provide fast cross-plane ion diffusion pathways, and meanwhile, the carbon nanocages with partially graphitic shells ensure the rapid electron transfer. The supercapacitor assembled with the optimized sample can deliver a high specific capacitance (up to 194 F/g at 1 A/g), superior rate capability (68% capacitance retention at 70 A/g), low IR drop (0.685 V at 70 A/g). Moreover, benefiting from the wide working voltage and high-rate capability, the energy densities can maintain at 56.1 Wh/kg even at an ultrahigh power density of 61.250 kW/kg. Strikingly, the as-assembled supercapacitor can successfully power a light-emitting diodes (LED, 2.2 V) module with 53 red LED lights demonstrating its great potential for practical applications in energy storage devices.

Modified electrochemical charge storage properties of h-BN/rGO superlattice through the transition from n to p type semiconductor by fluorine doping

A band gap of ∼2.1 eV was obtained through the hybridization of reduced graphene oxide (rGO) with insulating hexagonal boron nitride (h-BN). The h-BN/rGO superlattice behaved like n type semiconductor due to the enriched electron density at the conduction band and allowed charge transfer depending on the redox potential of the electrolyte. The band gap energy was further minimized to ∼1.79 eV through fluorine (F) doping within the h-BN/rGO. F doping created population density near the valance band and the Fermi level shifted towards the lower energy level. F doped superlattice behaved like p type semiconductor where F was adsorbed mostly at the N site. It is noticed that the contribution of the redox charge transfer to the overall capacitance was increased in comparison to the electrochemical double layer capacitance with increasing F doping. The formation of defects and disorder due to doping provided facile diffusion path enhancing the charge storage contribution from the interior site of the electrode materials. The specific capacitance of the F doped h-BN/rGO superlattice was determined as 1250 F g−1 which is 130% of un-doped sample. An asymmetric supercapacitor (ASC) cell was fabricated with F doped h-BN/rGO superlattice, which showed almost zero IR drop, high stability (∼77% retention of capacitance after 10,000 charge–discharge cycles) and large energy and power density of 87.5 W h kg−1 and 6300 W kg−1, respectively. Furthermore, the ASC also exhibited very low relaxation time constant of ∼0.39 ms ensuring effective power delivery and quick charge–discharge capacity.

All-solid-state flexible supercapacitor based on spray-printed polyester/PEDOT:PSS electrodes

ABSTRACTWe report on a one-step spray printing technique to fabricate large-area flexible electrodes using poly (3, 4-ethylene dioxythiophene)-polystyrene sulfonate (PEDOT:PSS) and polyester cloth. The H3PO4 treated PEDOT:PSS electrodes exhibit an enhanced capacitance, high rate capability and wide voltage window (0–1.6 V). The printed polyester/PEDOT:PSS electrode treated with H3PO4 exhibits a specific capacitance of ∼40 F g−1 at 40 mV s−1. A large area device exhibits a high iR drop of 0.23 V, which can be minimized using conducting materials such as carbon cloth or steel mesh in place of polyester cloth.

Impact of IR Drops on the −850 mVCSE Cathodic Protection Criterion for Coated Steel Pipes in Soil

AbstractBy means of numerical modeling and experimental measurements, this work addresses the longstanding controversy of whether or not IR (ohmic) drops need to be considered in on-potential catho...

The Effect of Deposition Conditions on Atmospheric Pitting Corrosion Location Under Evans Droplets on Type 304L Stainless Steel

Pit location during atmospheric corrosion of Type 304L stainless steel under MgCl2 droplets depends on initial droplet concentration. Pits formed predominantly in the center of the droplet for concentrations ≥4 M, closer to the perimeter for 1.5 M to 3 M, and were randomly distributed for concentrations ≤1 M. Pits initiated only after the droplets had evaporated to a critical concentration >3 M, where droplets deposited with lower initial concentrations were thinner. The results can be explained in terms of “differential aeration” and IR drop effects, showing that corrosion in “splash zones” may differ from that under aerosol salt deposit layers that deliquesce forming initially saturated solutions.

Engineered carbon fiber papers as flexible binder-free electrodes for high-performance capacitive energy storage

A binder-free electrode for flexible supercapacitor applications was fabricated using carbon fiber papers (CFPs) via a facile paper making method. CV curves and galvanostatic charge/discharge profiles exhibited ideal capacitive behavior and linear voltage–time function with small IR drop. O2 activation process greatly affected the porosity and surface structures. The CFP electrodes activated at 325°C for 45min by O2 oxidizing gas showed highest specific capacitance of 156.9Fg−1 and excellent cycle stability (∼90.2%) after 5000 cycles at 1.0Ag−1 in 1.0M H2SO4, which presented the possibilities as flexible electrodes with excellent electrochemical performances for EDLCs.

Crevice Corrosion of Stainless Steels 904L, 2205, and 2507 in High-Temperature Sulfuric Acid Solution Containing Chlorides: Influence of Metal Cations

Crevice corrosion influences the integrity of materials in many industrial sectors, such as hydrometallurgy. The conditions in hydrometallurgical processes are severe, with high concentrations of sulfuric acid leachant as well as high-chloride impurity, oxygen, and metal cation contents. In this study, crevice corrosion behavior of highly-alloyed austenitic and duplex stainless steels is investigated in aerated high-temperature sulfuric acid solution with 1 g/L chlorides in the presence of three types of metal cations: Fe3+, Cu2+, and Fe2+. The experimental work contains the determination of the oxidizing capacity of the solutions, immersion crevice corrosion tests followed by characterization of the corrosion attack, and potentiodynamic polarization measurements. The results show that the alloy with the highest PREN value, grade 2507, was not susceptible to crevice corrosion under the test conditions. In the case of grades 904L and 2205 of relatively equal PREN values, the extent and nature of crevice corrosion attack was different and dependent on the ratio of activities of chlorides to sulfates and the type of metal cations. The results are presented and discussed in the light of IR drop mechanism.

Fast Stochastic Analysis of Electromigration in Power Distribution Networks

A fast and stochastic analysis methodology for electromigration (EM) assessment of power distribution networks is presented in this paper. We examine the impact of variability on EM time-to-failure (TTF), considering altered current densities due to global/local process variations as well as the fundamental factors that cause the conventional EM TTF distribution. Through the novel variations-aware current density model based on Hermite polynomial chaos, we demonstrate significant margins in EM lifetime when compared with the traditional worst case approach. On the other hand, we show that the traditional approach is altogether incompetent in handling transistor-level local variations leading to significantly optimistic lifetime estimates for lower metal level interconnects of power delivery network. Subsequently, we attempt to bridge the conventional, component-level EM verification method to the system level failures, inspired by the extreme order statistics. We make use of asymptotic order models to determine the TTF for the kth component failure due to EM, and demonstrate application of this approach in developing IR drop aware system-level failure criteria.

An Economical Half-Cell and Modified Rotating Disk Electrode for Electrochemical Characterizations of Fuel Cell Catalyst-Coated Membranes and Gas Diffusion Electrodes

Common methods of fuel cell electrocatalyst characterization, in particular the oxygen reduction reaction (ORR) catalysts, include thin-film RDE and PEMFC measurements using fuel cell test stations. The former is generally available in many electroanalytical labs, however, ink deposition on RDE tips and limited solubility of oxygen in the electrolyte lead to testing environments which are quite different from those of fuel cell hardwares. The latter option requires fuel cell hardware and an appropriate test station which are expensive and not widely accessible by many labs. We present two approaches in order to bridge the gap between these methods: 1) a modified RDE tip which accepts catalyst-coated membranes (CCMs), thus eliminating the potential issues of catalyst ink deposition and the associated variabilities, and 2) a low-cost half-cell setup which allows fuel cell-like current densities (~ 1 A cm-2) to be obtained using gaseous oxygen feed. The novel RDE tip has been tested with Pt foil and commercial CCMs in 0.1 M HClO4 at room temperature (20°C) and good agreements with polycrystalline Pt and H2/O2 fuel measurements have been obtained, respectively. In addition, CCM degradation tests, using an accelerated degradation test protocol (ADT) with potential cycling, have been performed and the loss of Pt and Pt surface area have been quantified. With the half-cell setup, constant current polarizations with IR drop measurement at each step were found to provide a simple, reproducible method of measuring catalyst performance using an optimal electrolyte concentration of 1.0 M HClO4. Accurate ORR activity of commercial GDEs/CCMs and good agreement with measurements made in fuel cell hardware have been obtained with the half-cell setup. Both of these approaches are low cost (< $1000 USD) and can be implemented in a typical electroanalytical lab. Cells designs and results of ORR experiments with both approaches will be presented. Figure 1

A smart bottom-up strategy for the fabrication of porous carbon nanosheets containing rGO for high-rate supercapacitors in organic electrolyte

Exploration of various porous carbon materials with enhanced electrochemical performance is critical for the development of long-term sustainable energy storage and production systems. Herein, we have designed a smart bottom-up strategy to transformation of pitch into porous carbon nanosheets containing rGO (reduced graphene oxides) (PCSG) through a soft solution process coupling with KOH activation. This efficient solution process without involving hard templates or harmful solvents, which is clearly different from all the previously reported process, opening a new route towards porous carbons for energy storage applications. Notably, the as-obtained PCSG-60 sample (synthesized from 60mg of GO) presents an optimum integration of a large specific surface area of 2217m2/g, uniform micropore size (∼1.5nm), and sheet-like morphologies. When evaluated as electrode materials for supercapacitor in 1M TEABF4/AN electrolyte, the PCSG-60 exhibits excellent capacitive performance including large specific capacitances of 221F/g (at 1A/g), considerable rate capability (71.9% capacitance retention from 1A/g to 50A/g), smaller IR drop (0.637V at 50A/g), good cycling stability (91.8% of the initial capacitance after 3000 cycles at 10A/g) and an energy density up to 38.2 Wh/kg even at an ultrahigh power density of 40500W/kg, which puts the PCSG-60 among the best electrochemical performance in the reported pitch-derived carbon electrodes for supercapacitors. The outstanding capacitive electrochemical performance combined with the low-cost and readily accessible precursors enable the PCSG-60 is a promising electrode material for supercapacitor and other electrochemical energy storage system applications.

NiCo2S4@PPy core-shell nanotube arrays on Ni foam for high-performance supercapacitors

NiCo2S4@PPy core–shell nanotube arrays have been successfully prepared through three facile steps: solvothermal synthesis, solvothermal sulphurisation and subsequent in situ electropolymerisation of polypyrrole (PPy). Their structure and morphology were studied by XRD, FTIR, SEM and TEM. The results suggest that a thin layer of PPy with 8 nm in thickness is wrapped on the surface of NiCo2S4 nanotubes. The coating PPy strong promotes pseudo-capacitance reaction of NiCo2S4 nanotube arrays. NiCo2S4@PPy shows lower charge plateau and IR drop, higher discharge plateau and Coulombic efficiency. Rate performance is improved remarkably. Average specific capacitance at 24 mA cm−2 is even two times that of the uncoated NiCo2S4. The galvanostatic cycling tests at 4 mA cm−2 indicate NiCo2S4@PPy exhibit the highest specific capacitance of 1524 F g−1 and improved capacitance retention to 78.5% after 3000 cycles. The corresponding values of the uncoated NiCo2S4 nanotube arrays are only 1410 F g−1 and 22%. The improved electrochemical performance is mainly attributed to unique core–shell nanotube array structure and the key assistant effect of the coating PPy which remarkably improves the conductive property of NiCo2S4 long nanotubes and effectively enhances structure stability and cycling stability of NiCo2S4 nanotubes.

Improving Performance under Process and Voltage Variations in Near-Threshold Computing Using 3D ICs

Near-threshold computing (NTC) circuits have been shown to offer significant energy efficiency and power benefits but with a huge performance penalty. This performance loss exacerbates if process and voltage variations are considered. In this article, we demonstrate that three-dimensional (3D) IC technology can overcome this limitation. We present a detailed case study with a 28nm commercial-grade core at 0.6V operation optimized with various 3D IC physical design methods. First, our study under the deterministic case shows that 3D IC NTC design outperforms 2D IC NTC by 29.5% in terms of performance at comparable energy. This is significantly higher than the 12.8% performance benefit of 3D IC at nominal voltage supplies due to higher delay sensitivity to input slew at lower voltages. Second, it is well demonstrated that transistor delay is more sensitive to voltage changes at NTC operation. However, our full-chip study reveals that IR drop effect on 2D/3D IC NTC performance is not severe due to the low power consumption and hence lower IR drop values. Third, die-to-die variation impact on full-chip performance is visible in 3D IC NTC designs, but it is not worse compared to 2D IC NTC designs. This is mainly due to the shorter critical path length in 3D IC NTC designs.

Full Chip Impact Study of Power Delivery Network Designs in Gate-Level Monolithic 3-D ICs

In this paper, we present a comprehensive study on the impact of power delivery network (PDN) on full-chip wirelength, routability, power, and thermal effects in gate-level monolithic 3-D (M3-D) ICs across different technology nodes. Our studies show that PDN worsens routing congestion more severely in M3-D ICs than in 2-D designs due to the significant reduction in resources for 3-D connections. The relative impact worsens at advanced technology nodes due to higher congestion of interconnects. The increase in signal wirelength translates into additional net switching power dissipation, which significantly contributes to total power. This in turn aggravates thermal issues further in 3-D ICs. In addition, we observe that PDN tradeoffs among wirelength, power, and thermal are more pronounced in M3-D ICs than through silicon via-based 3-D and 2-D designs because of the higher integration density and the severe competition between signal and power connections. We also compare the impact of PDN on full chip routing in M3-D ICs versus face-to-face 3-D ICs. Lastly, we use various PDN design optimization techniques for M3-D ICs at different nodes and obtain up to 13.9% signal wirelength and 17.6% total power reduction under the given IR drop budget.

Particle size effect in porous film electrodes of ligand-modified graphene for enhanced supercapacitor performance

Graphene-based electrodes for high performance supercapacitors are developed by taking advantage of particle size control, large mass loading, and surface functionalization of reduced graphene oxide (rGO) sheets. Two controlled sizes of graphene sheets (100 nm vs. 45 μm average lateral dimensions) were prepared to study two-electrode system performance. The nano-size graphenes led to the formation of mesoporous films, resulting in higher capacitance, better capacitance retension and lower equivalent series resistance (ESR), indicating better surface usability for diffusion and accessibility of electrolyte ions by shortening transport paths (compared with horizontally stacked films from micro-sized graphenes). For studies using an aqueous electrolyte, the maximum specific capacitance of nano-rGO film was 302 F/g (at 1 A/g with 4.3 mg/cm2 of mass loading), which was ∼2.4 times higher than micro-rGO film, and achieved a ∼67% reduced ESR. With an organic electrolyte, the nano-rGO delivered ∼4.2 times higher capacitance (115 F/g at 2 A/g with 4.3 mg/cm2), 4.0 times lower IR drops, and an order-of-magnitude lower charge-transfer resistance with an energy density of 18.7 Wh/kg. The results of this work indicate that the size control of graphene sheet particles for film deposit electrodes can be a simple but effective approach to improve supercapacitor performance.

Some Extensions of the Galvele Approach to Localized Corrosion, Including the Effect of Cation Complexation

Analytical and numerical modeling have been used to extend the understanding of pitting corrosion in a one-dimensional geometry. The approach is based on that of Galvele [1] and later experimental studies that supported many of Galvele’s findings [2], but with more detail and new features. We have examined both ideal solutions, and non-ideal solutions where the diffusivity (D) is a function of concentration (c) for any species, as well as cation complexation by chloride. The essential result that Galvele obtained was: Epit = A – B log [NaCl], where Epit is the pitting potential and B should be 0.059 V at 298 K. Laycock and Newman [2] clarified that the quantity A contained the kinetics of the anodic dissolution reaction, and defined a quantity that they called the transition potential, ET, which is the potential where the anodic current density i becomes equal to the anodic limiting current density, iL. The origin of Galvele’s equation is an analytical solution of the governing reaction-transport equation (Nernst-Planck equation) considering an unreacting ion such as Cl-. In this solution, as refined by Newman [3], the second term in Galvele’s equation is the IR drop in the pit at the limiting current density iL. Importantly, iL depends on [NaCl] because the contribution of migration to the outward flux of dissolved metal cations increases as [NaCl] decreases. In the present work, we have examined the following refinements, with the following preliminary outcomes: The variation of B with [NaCl] – B is constant at 0.059 V over a certain range of [NaCl], but decreases at high [NaCl]. This is easily understood physically. At low [NaCl] there appear to be small deviations from 0.059 V that are still under investigation. The effect of introducing a D(c) – this turned out to be an intriguing area of study, and new results will be presented at the meeting. Briefly, the effect of varying diffusivity is not as great as might be assumed. Cation complexation – this is the latest aspect to be investigated. Changes in B with complexation are expected. Such changes may explain the different empirical values of B found in different materials including stainless steels.