Accelerated Degradation Test Research Articles

Optimal design of step-stress accelerated degradation tests based on genetic algorithm and neural network

In this study, the optimal design of step-stress accelerated degradation tests is focused. An optimization model is proposed where an improved accelerated degradation model is involved to comprehensively consider the influence of accelerated stress and the measurement error. Then, a novel optimal design method is constructed, where multiple decision variables can be simultaneously optimized based on neural network and genetic algorithm. An effective sensitivity analysis method is further established to quantitively illustrate the influence of the predetermined model parameters on the optimal results. Finally, a case study is implemented, and a series of comparisons are implemented to demonstrate the effectiveness and rationality of the proposed method.

In-Site Grown NiFeOOH Nanosheets Foam Directly as Robust Electrocatalyst for Efficient Urea Oxidation Application.

In this work, a series of morphology controlled NiFeOOH nanosheets were directly developed through a one-step mild in-situ acid-etching hydrothermal process. Benefiting from the ultrathin interwoven geometric structure and most favorable electron transport structure, the NiFeOOH nanosheets synthesized under 120 ˚C (denoted as NiFe_120) exhibited the optimal electrochemical performance for urea oxidation reaction (UOR). An overpotential of merely 1.4 V was required to drive the current density of 100 mA cm-2, and the electrochemical activity remains no change even after 5000 cycles accelerated degradation test. Moreover, the assembled urea electrolysis set by using the NiFe_120 as bifunctional catalysts presented a reduced potential of 1.573 V at 10 mA cm-2, which was much lower than that of overall water splitting. We believe this work will lay a foundation for developing high-performance urea oxidation catalysts for the large-scale production of hydrogen and purification of urea-rich sewage.

A General Degradation Process of Useful Life Analysis Under Unreliable Signals for Accelerated Degradation Testing

In order to achieve fault diagnosis and prognosis, one needs a sufficient and valid life-cycle data. However, this requirement is difficult for current high-reliable manufacturing system. Good thing is that the technique of accelerated degradation testing can be used to address this issue. Bad thing is that, it needs a reliable testing/measuring technique to build an accurate model for accelerated degradation testing. However, in practical applications, data acquisition is obtained by sensors or measurement devices, which cannot guarantee perfect working condition under the influence of external environment and stresses, resulting in unreliable signals. Furthermore, since traditional models require complex differentiation and cannot obtain analytical expressions when considering unreliable signals, traditional models rarely reflect well this situation. Motivated by these facts, an accurate model for the accelerated degradation testing is proposed in this study with considering the unreliable signals. Based on the proposed model, a closed-form expression for the useful life analysis is derived. The M-H sampling method is used to estimate the unknown parameters used in the proposed model. For illustration, the electrical connectors dataset is analyzed with the proposed model and the traditional models. Comparing the obtained results, the proposed model is more accurate in the useful life analysis than the traditional accelerated degradation testing models by considering the unreliable signals.

Comparative Study on the Organic Solvent of IrO2–Ionomer Inks used for Spray Coating of Anode for Proton Exchange Membrane Water Electrolysis

Currently, spray coating has attracted interest in the mass production of anode catalyst layers for proton exchange membrane water electrolysis (PEMWE). The solvent in the spray ink is a critical factor for the catalyst dispersion in ink, the microstructure of the catalyst layer, and the PEMWE performance. Herein, various pure organic solvents were examined as a substitute for conventional isopropanol-deionized water (IPA-DIW) mixture for ink solvent. Among the polar solvents that exhibited better IrO2 dispersion over nonpolar solvents, 2-butanol (2-BuOH) was selected as a suitable candidate. The PEMWE single cells were fabricated using 2-BuOH at various ionomer contents, spray nozzle types, and drying temperatures, and their performance was compared to the cells fabricated using a conventional IPA-DIW mixture. The PEMWE single cells with 2-BuOH solvent showed good performances comparable to the conventional IPA-DIW mixture case and highly durable performances under accelerated degradation tests.

A Novel Model Validation Method Based on Area Metric Disagreement between Accelerated Storage Distributions and Natural Storage Data

It has been a challenge to quantify the credibility of the accelerated storage model until now. This paper introduces a quantitative measurement named the CMADT (Creditability Metric of Accelerated Degradation Test), which quantifies the credibility of the accelerated aging model based on available data. The relevant criterion data are obtained from the natural storage test. CMADT is a credibility metric obtained by measuring the difference in the metric area between the probability distribution of the accelerated storage model and its criterion data. In addition, the accelerated aging model might include multiple parameters resulting in several single-parameter CMADTs. This paper proposes a method that integrates several single-parameter CMADT metrics into a single metric to assess the overall credibility of the accelerated storage model. Moreover, CMADT is universal for different scales of sample data. The cases addressed in this paper show that CMADT helps designers and decision-makers judge the credibility of the result obtained by the accelerated storage model intuitively and makes it easier to compare various products horizontally.

Ni / GDC Fuel Electrode for Low Temperature SOFC and its Aging Behavior under Accelerated Stress

The microstructural integrity of Ni-based fuel electrodes is mandatory for long term SOFC operation. Degradation due to microstructural changes as Ni-agglomeration, sintering and densification has to be prevented by an appropriate microstructure. In this work the performance of 4 types of nickel-ceria based fuel electrodes, which differ with respect to layer sequence and manufacturing processes, is evaluated by electrochemical impedance spectroscopy at the nominal operating temperature of 600 °C. Accelerated degradation tests at increased operating temperatures of 700 °C and 900 °C are performed on the one based on a GDC infiltrated Ni-backbone that performed the best. The polarization resistance at 600 °C recorded at the beginning and the end of life increased by up to 100%. Microstructural analysis of the electrodes at different aging states revealed strong microstructural changes of fine infiltrated GDC structures and Ni agglomeration at higher operating temperature.

Performance Enhancement of Polymer Electrolyte Membrane Fuel Cells with Cerium Oxide Interlayers Prepared by Aerosol-Assisted Chemical Vapor Deposition

In this study, the performance and durability of a Pt/CeOx catalyst membrane electrode assembly (MEA) fabricated by chemical vapor deposition and sputtering using aerosols were investigated for use in a polymer electrolyte membrane fuel cell (PEMFC). The cost burden of Pt-based catalysts and the degradation of performance and durability owing to corrosion of the carbon support under certain conditions limit the commercialization of PEMFCs. To solve these problems, the development of Pt alloy catalysts (Pt–Co, Pt–Ni, and Pt–Fe), Pt-based core–shell catalysts (Pt–TiO2 and Pt–CeO2), Pt bimetallic catalysts (Pt–Pd, Pt–Ru, and Pt–Sn), and Pt-based nanocomposites (Pt/graphene and Pt/carbon nanotubes) is being actively researched. Inserting a CeOx interlayer between Pt and carbon has three advantages: (i) oxygen supply to Pt due to CeOx interlayer’s ability to store oxygen improves catalyst utilization, (ii) improves the dispersibility of Pt, and (iii) solves the problem of performance and durability degradation by preventing the formation of reactive intermediates. For the deposition of ceria, the aerosol-assisted chemical vapor deposition process, which is performed at atmospheric pressure and can be uniformly deposited over a wide area with spray-based precursor delivery characteristics, was applied. The performance and electrochemical surface area of the Pt/CeOx MEA were determined using I–V measurements and cyclic voltammetry, and the durability of the Pt/CeOx MEA was analyzed using electrochemical impedance spectroscopy and an accelerated degradation test. As a result, when the Pt/CeOx on the gas diffusion layer (GDL) MEA was used, the performance improved by 46% compared to that of Pt on the GDL.

Configuration-Dependent Oxygen Reduction Reaction Performance of Iridium-Decorated Ni@Pd Nanocatalysts

The widespread market introduction of fuel cells is severely restricted by the sluggish oxygen reduction reaction (ORR) kinetics at the cathode side, which demands highly efficient and durable catalysts for generating adequate rates. By keeping this in view, herein, we report a systematic study to unveil the effect of structure configuration on the ORR activity of tri-metallic nanocatalysts (NC)s comprising atomic iridium (Ir) cluster (0.5 wt % of Ir)-anchored Pd nanoparticles (NP)s on the tetrahedral symmetric Ni-oxide support (denoted as NPI), prepared via a temperature-controlled wet chemical reduction method. For the optimum condition when the impregnation temperature for Ni-crystal growth is 40 °C, the Ir-cluster-decorated Ni@Pd nanoislands are formed (hereafter denoted as NPI-40), outperforming the commercial Johnson Matthey-Pt/C (J.M.-Pt/C; 20 wt % Pt) catalyst by 181-fold with an unprecedented high mass activity of 12,163 mAmgIr–1 at 0.85 V vs RHE in alkaline ORR (0.1 M KOH). More importantly, NPI-40 NC retained 100% ORR performance with no degradation up to 20,000 accelerated degradation test (ADT) cycles, while only a 5 mV loss in half-wave potential (E1/2) is observed after 30 k ADT cycles. Besides, Ir-cluster-decorated Nicore@unconformable Pdshell and Ni-to-Pd epitaxial structures are formed at 25 °C (NPI-RT) and 70 °C (NPI-70) impregnation temperatures, respectively, showing the significantly decreased mass activities of 997 and 5146 mAmgIr–1 at 0.85 V vs RHE. The results of physical structure inspections and electrochemical analysis suggest that such an exceptional ORR performance of NPI-40 NC originates from the potential synergism between the high density of the occupied Ir-d orbital and the adjacent compressively strained Ni–Pd interface, where Ir sites offer optimal adsorption energy for O2 splitting and the Ni–Pd interface facilitates the subsequent desorption of hydroxide ions (OH–). We believe that the obtained results will open new avenues for the facile design of Pt-free NCs for fuel cell cathodes and will benefit fuel-cell technology via both ecologically and economically friendly means.

Highly accessible platinum with low-loading embedded in hierarchically porous carbon fiber for efficient oxygen reduction reaction

Improving the utilization efficiency of platinum (Pt) is required for realizing the efficient oxygen reduction reaction (ORR) in rechargeable Zn–air battery (ZAB). Herein, a carbon fiber decorated with coexistence of uniformly dispersed Pt nanoparticles and Pt-N-C moieties (Pt-HPCF) is synthesized and used as electrocatalyst for ORR. The elaborately structural design of Pt-HPCF catalyst on atomic/nanoscopic, mesoscopic and macroscopic level guarantees highly accessible activity sites, fast reactants transport, rapid electron transfer, and strong metal-support interaction. Benefited from the multi-level synergistic optimization, this unique Pt-HPCF electrocatalyst with ultralow Pt loading presents excellent ORR activity with a mass activity of 912.08 mA mg−1 at 0.85 V, which is 7.5 times that of the corresponding value for commercial Pt/C catalyst. Moreover, Pt-HPCF also exhibits high stability after accelerated degradation test. Furthermore, ZAB assembled with Pt-HPCF catalyst exhibits a high open circuit voltage (OCV) of 1.576 V, high capacity of 840 mAh g−1 at 5.0 mA cm−2, and a large peak power density of 163.38 mW cm–2. This work provides a feasible route for optimizing the Pt or other metal-based electrode in energy storage/conversion fields.

A 5-V Switch for Analog Multiplexers With 2.5-V Transistors in 28-nm CMOS Technology

Despite the scaling of the supply voltage of deep-submicrometer CMOS technologies, many applications still require to deal with off-chip signals in high-voltage domains (e.g., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.3$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~ \mathrm{V})$</tex-math> </inline-formula> . Hence, foundries offer fabrication processes with voltage-tolerant transistors, which are inherently protected from the electrical stress, at the expenses of compromising their performances, reducing the design portability, and augmenting the production costs in case of the customization of the process. As an alternative, circuit techniques, such as cascoding, adaptive biasing, and voltage shifting, result effective in designing analog circuits, such as amplifiers and voltage drivers at high supply voltage with voltage-scaled transistors. This article presents the architecture of a switch for analog multiplexers (MUXs) able to handle signals up to twice the nominal supply voltage of the employed transistors. To validate the circuit choice, a switch for a 5-V MUX has been designed with 2.5-V transistors in 28-nm CMOS technology. The comparison with a benchmark architecture with tailored 5-V devices shows that an about three times larger area and 4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> A static current demand have to be considered. Moreover, an accelerated degradation test (ADT) showed a similar decay of the features of both types of switches.

Strategic Approaches for Assessing the Reliability Information during Product Development: Perspective of the Partially Accelerated Degradation Test

In this paper, a strategic approach is provided for simultaneously assessing the verification and validation (V&amp;V) test results and the reliability information during product development based on the perspective of the partially accelerated degradation test (PADT) scheme. This approach addresses the obstacle of obtaining prior information on the model parameters for conducting PADT while minimizing the asymptotic variance of the acceleration model parameters. The strategic advantages and characteristics of the PADT, which do not exist in the classical accelerated test (AT) and partially accelerated test (PAT), are presented. In addition, the advantages and suitability of adopting the PADT instead of the partially accelerated life test (PALT) for effectively assessing the reliability information during product development are investigated through illustrative examples.

Improving stability of reinforced composite membrane with hydrophilic interlayer coating

Coating a reinforced composite membrane with a hydrophilic Pt layer can substantially improve the durability of polymer membranes used in fuel cell applications. In this study, we investigated the performance and durability of Aquivion/expanded polytetrafluoroethylene (ePTFE)-reinforced composite membranes with varying Pt contents. We introduced a Pt coating onto ePTFE via magnetron sputtering and characterized the Pt layer using scanning electron microscopy and X-ray photoelectron spectroscopy. As the amount of Pt coating increased, the surface of ePTFE became more hydrophilic; thus, the Pt-impregnated composite membrane was better than the bare composite membrane. We evaluated the fuel cell performance through a single-cell test following membrane electrode assembly fabrication, and performed an accelerated degradation test by maintaining the cell at an open circuit voltage at 90 °C and low humidity (30% relative humidity) for 144 h. Compared to the pure composite membrane, the Pt-coated composite membrane showed less degradation and a lower fluorine emission rate. These results indicated that Pt-coated composite membranes are potentially suitable candidates for use in proton exchange membrane fuel cells.

Durability and Thermal Behavior of Functional Paints Formulated with Recycled-Glass Hollow Microspheres of Different Size.

This study aims to assess the effect of hollow glass microspheres of different sizes derived from glass industry waste on the durability and thermal behavior of waterborne paint. The coatings were characterized by electron microscopy to investigate the distribution of the spheres and their influence on the layer morphology. The impact of the various glassy spheres on the mechanical feature of the coatings was assessed using the Buchholz hardness test and the Scrub abrasion test. The role of the spheres in altering the durability of the samples was analyzed by the salt spray exposure test and the electrochemical impedance spectroscopy measurements. Finally, a specific accelerated degradation test was carried out to explore the evolution of the thermal behavior of the composite coatings. Ultimately, this work revealed the pros and cons of using hollow glass spheres as a multifunctional paint filler, highlighting the size of the spheres as a key parameter. For example, spheres with adequate size (25-44 µm), totally embedded in the polymeric matrix, are able to reduce the thermal conductivity of the coating avoiding local heat accumulation phenomena.

Cover Picture: Materials and Corrosion. 3/2023

Cover: There are concerns about the acid of refrigerant oils (inside piping) and corrosion by the salts in seawater (outside piping) for industrial piping. Corrosion-resistant characteristics of various aluminum alloys were investigated by accelerated degradation tests with changing storage conditions, such as temperature and atmosphere. The results from immersion tests in a refrigerant and cyclic corrosion tests (intermittent cycles between salt mist and drying) proved that aluminum alloys can be used for refrigerant piping. More detailed information can be found in: Seiji Uchiyama, Satoshi Uemura, Koji Hiraoka, Yuji Kimura, Shiro Seki, Corrosion and degradation behavior of aluminum and copper refrigerant piping, Materials and Corrosion 2023, 74, 344.

Estimating remaining useful life of rotating machinery using relevance vector machine and deep learning network

In today’s manufacturing industry, unexpected equipment failure caused by mechanical degradation usually leads to serious losses in availability, reliability, quality, and cost. To handle the issues of fault diagnosis and remaining useful life (RUL) prediction for rotating machinery, this contribution presents a multi-technique fused method for health prognostics using relevance vector machine (RVM) and deep separable convolutional gated recurrent network (DSCGRN). The proposed data-driven method gets rid of handcrafted feature extraction and considers multi-sensor data and their temporal dependencies at different degradation states. Specifically, the method is implemented in two phases: anomaly detection and RUL prediction. In the first phase, a RVM classifier, which distinguishes the state of mechanical degradation as no-obvious-fault-tendency and fault-prone, provides a fault threshold for the full-life-cycle degradation progressions and enables the method to concentrate more on fault-prone stage. In the second phase, a regression estimator (i.e., DSCGRN) is shaped to learn deep-layer feature representation from the raw multi-sensor data, thus accurate RUL estimation can be carried out, especially for the fault-prone condition. The proposed method is validated through the raw multi-sensor data of bearings accelerated degradation tests. It turns out that the proposed method performs superiority in RUL prediction compared with some existing prognostic approaches.

Isothermal crystallization process and thermal analysis of polylactic acid/cotton fiber composites during thermal degradation

ABSTRACT The effects of reactive and non-reactive surface treatment agents on the isothermal crystallization rate and subsequent melting behavior of polylactic acid/cotton fiber (PLA/COF) composites before and after accelerated degradation testing at 60°C for 2000 h were demonstrated. The results showed that the crystallization rate of PLA was rapidly accelerated by the incorporated COF, while the use of epoxy-based reactive surface treatment agents inhibited the movement of PLA molecular chains and reduced the crystallization rate and melting point of the PLA/COF. These results suggest that the reactivity of the agent affects the crystallization behavior of the composite during long-term use.

Degradation mechanism of all‐solid‐state lithium‐ion batteries with argyrodite Li7−xPS6−xClx sulfide through high‐temperature cycling test

AbstractSulfide‐based all‐solid‐state lithium‐ion batteries (LIBs) are promising replacements for conventional liquid electrolyte LIBs. However, their degradation mechanisms and analysis methods are poorly understood. Herein, the degradation mechanism of an argyrodite‐type sulfide‐based all‐solid‐state prototype LIB cell is reported. Furthermore, an analysis method for all‐solid‐state batteries using charge/discharge cycle tests at 100°C followed by the disassembly analysis of cells before and after accelerated degradation tests is reported. Based on the findings of this study, the degradation of the prototype cell is classified as follows: (i) solid electrolyte (SE) oxidation in the positive electrode, which recovers battery capacity and increases resistance; (ii) SE reduction in the negative electrode, which decreases capacity; (iii) lithium deposition on/in the negative electrode, which decreases capacity; and (iv) capacity loss of the positive electrode, which decreases capacity. These degradation reactions appear to occur simultaneously. These findings are expected to aid the development of sulfide‐based solid‐electrolyte LIBs with improved safety and energy densities.

Probabilistic State of Health and Remaining Useful Life Prediction for Li-Ion Batteries

Lithium-ion batteries are widely used in electric vehicles due to their high specific energy value. The continuous charge/discharge cycles pf batteries, determining a change of their State of Health (SoH) and a reduction of their Remaining Useful Life (RUL). The relevant literature describes a variety of methods for the prognostic of battery degradation and RUL estimation, based on electrochemical models or on statistical and artificial intelligence techniques. However, the capacity degradation of lithium-ion batteries depends on many uncertain parameters that are suitable to be estimated and modeled within a probabilistic framework. Therefore, the development of new probabilistic methodologies for the prognostic of lithium-ion batteries can be useful and effective. In this paper, probabilistic models based on time series (AutoRegressive Integrated Moving Average model with eXogenous predictors, (ARIMAX)) and regression approaches (Linear Quantile Regression (LQR), Bootstrap Multiple Linear Regression (B-MLR) and Bayesian Bootstrap Multiple Linear Regression (BB-MLR)) are developed and compared for this purpose. All the considered models are specifically suited up to exploit data coming from Accelerated Degradation Tests (ADTs), and developed under two different approaches (i.e., non-differentiation and differentiation of the target time series) to predict SoH and RUL. Moreover, a dedicated procedure to extract a single, point value from the probabilistic predictions is presented to let the models work also in deterministic scenarios. The performance and the comparison between the proposals and several benchmarks taken from the literature are carried out using data from publicly available databases, confirming the validity and the accuracy of the proposed solutions.

Reliability assessment of permanent magnet brake based on accelerated bivariate Wiener degradation process.

Permanent magnet brake (PMB) is a safe and effective braking mechanism used to stop and hold the load in place. Due to its complex structure and high reliability, assessing the reliability of PMB remains a challenge. The main difficulty lies in that there are several performance indicators reflecting the health state of PMB, and they are correlated with each other. In order to assess the reliability of PMB more accurately, a constant stress accelerated degradation test (ADT) is carried out to collect degradation data of two main performance indicators in PMB. An accelerated bivariate Wiener degradation model is proposed to analyse the ADT data. In the proposed model, the relationship between degradation rate and stress levels is described by Arrhenius model, and a common random effect is introduced to describe the unit-to-unit variation and correlation between the two performance indicators. The Markov Chain Monte Carlo (MCMC) algorithm is performed to obtain the point and interval estimates of the model parameters. Finally, the proposed model and method are applied to analyse the accelerated degradation data of PMB, and the results show that the reliability of PMB at the used condition can be quantified quite well.

Reliability inference and remaining useful life prediction for the doubly accelerated degradation model based on Wiener process

&lt;abstract&gt;&lt;p&gt;Degradation data are an important source of products' reliability information. Though stochastic degradation models have been widely used for fitting degradation data, there is a lack of efficient and accurate methods to get their confidence intervals, especially in small sample cases. In this paper, based on the Wiener process, a doubly accelerated degradation test model is proposed, in which both the drift and diffusion parameters are affected by the stress level. The point estimates of model parameters are derived by constructing a regression model. Furthermore, based on the point estimates of model parameters, the interval estimation procedures are developed for the proposed model by constructing generalized pivotal quantities. First, the generalized confidence intervals of model parameters are developed. Second, based on the generalized pivotal quantities of model parameters, using the substitution method the generalized confidence intervals for some interesting quantities, such as the degradation rate $ \mu_0 $, the diffusion parameter $ \sigma_0^2 $, the reliability function $ R(t_0) $ and the mean lifetime $ E(T) $, are obtained. In addition, the generalized prediction intervals for degradation amount $ X_0(t) $ and remaining useful life at the normal use stress level are also developed. Extensive simulations are conducted to investigate the performances of the proposed generalized confidence intervals in terms of coverage percentage and average interval length. Finally, a real data set is given to illustrate the proposed model.&lt;/p&gt;&lt;/abstract&gt;