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Chemical and thermal characterization (FTIR-ATR, Soxhlet extraction, DSC) of polymeric encapsulants (EVA, POE, EPE) aged under accelerated aging conditions containing an UV source.
A unique accelerated aging humidity chamber for simulating the natural aging process of nuclear grade high efficiency particulate air (HEPA) filter media is being designed, implemented, and tested. The nuclear industry currently lacks information regarding the shelf life and service life of HEPA filter media. The Department of Energy recommends disposing of HEPA filters 10 years after the manufacture date for filters operated under dry conditions. Studies have shown the tensile strength and water repellency of HEPA filter media diminish with age. The chamber's principal function is to sustain an elevated relative humidity condition for an extended duration specified by the Arrhenius aging model. To accomplish this, various design parameters were established: (1) consistently achieve uniform humidity conditions within the chamber to equally expose media sheets, (2) ensure the chamber is sufficiently sealed to mitigate the uncontrolled infiltration of air, (3) confidently secure the media sheets to avert the introduction of unnecessary stressing/creasing, (4) fabricate the chamber from clear polycarbonate material to allow inspection of the media sheets, (5) provide a safe and ergonomic design for personnel, (6) ensure the chamber design is replicable and relatively easy to fabricate/assemble. A humidity source, fan, PID controller, humidity and temperature transmitters, and data loggers are required for proper operation and control of the chamber. The humidity source must accommodate target values up to 95% relative humidity throughout the chamber. The three humidity and temperature transmitters are strategically spaced throughout the chamber to ensure uniform conditions. The 10 cubic feet per minute (CFM) fan selected intends to accomplish the desired air change rate inside the chamber of approximately 20 air changes per hour (ACH). The 2 plenums on the upper and lower portions of the chamber utilize a perforated design to uniformly distribute air, promote air mixing, and control the air velocity entering the chamber. Industrial blueprint hanging clamps are being retrofitted to be seated within the chamber drawers and firmly secure the nuclear grade filter media. The aged media will be evaluated using autopsy methodology, and the results obtained intend to help clarify the useful life of nuclear grade HEPA filters. Nuclear grade high efficiency particulate air (HEPA) filters are defined as disposable, extended-media, dry-type filters with a rigid casing enclosing the full depth of the pleats and have a minimum particle removal efficiency of 99.97%. [1] - HEPA filters are constantly exposed to stressors and subsequently have been shown to degrade as the filter ages. Properties such as tensile strength and water repellency, along with others, are negatively impacted. [2] - Due to the scarcity of naturally aged HEPA filters available, it is crucial to develop accelerated aging methods which effectively mimic the natural degradation effects. - After accelerated aging, the filters are subject to testing in the Axial Flow Large Scale Test Stand (ALSTS) and other analysis techniques such as the same qualification tests performed directly after being manufactured. - Quality data is necessary for future decisions regarding the lifetime of nuclear grade HEPA filters. - The objective is to develop a prototype accelerated aging humidity chamber for nuclear grade HEPA filter media. The chamber should expose the media to commonly occurring stressors to expedite the degradation process caused by aging. PID yields reliable and reproducible results: - CFD model correlates well with actual performance; - Further analysis is needed to complete characterization; - Future work for the chamber is still to be completed. The data shown in Figure 5 and Table 1 indicate the system is functioning as designed. As can be determined from the system response evaluation in Table 1, the PID controller is yielding reliable and reproducible results at each set point. As the set point increases, the time constant and 20% settling time increase accordingly. From the results in Table 1, it stands to reason that the CFD model correlates well with the actual performance of the system. Each system response parameter for the 90%RH* CFD model is slightly lower than the parameters collected from the physical model tested at an equivalent set point. This is to be expected considering the inlet in the CFD model is a constant supply of water vapor, whereas the physical model uses a PID controller to monitor the amount of water vapor needed and reacts accordingly. More analysis is still to be done on the prototype chamber. A pressure test will be conducted in order to determine the hourly leak rate of the chamber. This test will involve constant air flow into the chamber until the desired pressure is reached. A uniformity test will also be conducted in order to ensure each filter medium is being exposed to equivalent relative humidity levels. This test will involve an array of humidity meters strategically oriented inside the chamber to record any possible gradients. Future work for the chamber includes dehumidification abilities, tests while fully loaded with filters, and temperature control. Once completed, the autopsy team at Institute of Clean Energy Technology will conduct necessary accelerated aging studies as needed.
Gel permeation chromatography analysis of the uncrosslinked portions of polymeric encapsulants (EVA, POE, EPE) aged under thermal accelerated aging conditions (in the absence of UV) is not a reliable way to measure encapsulant crosslinking nor degradation
Chemical and thermal characterization (FTIR-ATR, Soxhlet extraction, DSC) of polymeric encapsulants (EVA, POE, EPE) aged under thermal accelerated aging, without the presence of a UV source
This laboratory analytical procedure covers the accelerated aging of fast pyrolysis bio-oils. Bio-oils undergo reactions that result in physical and chemical changes over time. These changes typically result in an increase in molecular weight, decrease in some functional groups such as carbonyls, and an increase in viscosity; additionally, the aging process often leads to phase separation. Studies have shown that accelerated aging of bio-oils using this method closely mimics room temperature aging for long periods of time (over 3 years). This procedure has been developed for the accelerated aging of fast pyrolysis bio-oils only. Fast pyrolysis bio-oils are more reactive than other bio-oils (e.g., catalytic fast pyrolysis) and undergo aging much more rapidly. Therefore, this procedure should only be used for fast pyrolysis bio-oil samples.
Lithium metal batteries (LMBs) are prime candidates for next-generation energy storage devices characterized by their remarkable energy storage capabilities. Despite the importance of understating the calendar aging impacts in LMBs, cycle life and calendar life have received inconsistent attention across various research and development stages. For acceptance into an application, especially electric vehicles, batteries are required to have sufficient calendar life to ensure performance over the life of vehicles which often experience extended periods of inactivity. In this study, an in-depth exploration into the calendar aging of LMB (Li/ Li[Ni 0.8 Mn 0.1 Co 0.1 ]O 2 in pouch cell format) is conducted. Specifically, the impact of calendar aging factors, state-of-charge (SOC), temperature, pressure, and operating conditions (open-circuit voltage, OCV and constant voltage, CV) on the surface morphology and thickness change rate in lithium metal anode is investigated. Notably, the results show that storing LMB pouch cells at an OCV, 80 % SOC, 25 °C, and 10 psi external pressure leads to a <1% reduction in capacity over 18 months. The results also suggest routes which can be utilized in the future for accelerated aging without altering the primary degradation modes. The results also show an accelerated calendar aging at high temperatures (45 °C), 100 % SOC, and CV suggesting they may serve as key accelerated aging methods for future studies. During calendar aging, pressure mitigates dendrite growth and extends calendar life. In conclusion, the insights from this study reinforce the viability of LMBs as a compelling solution for addressing increased energy storage needs in real-world applications.
Degradation of photovoltaic (PV) module encapsulant mechanical characteristics that lead to embrittlement and delamination remains a cause of failure in solar installations. A multiscale reliability model based on detailed molecular degradation reaction kinetics was previously published, connecting the encapsulant mechanical properties (elastic modulus, yield strength, and adhesion energy) to the degraded molecular structure and interfacial bond density to adjacent solar cell and glass substrates. The model, developed primarily for poly(ethylene-co-vinyl acetate) (EVA) encapsulants, remains to be experimentally validated. Determining the degradation and crosslinking kinetics of alternative encapsulants, such as polyolefin elastomer (POE) and EVA/POE/EVA composites (EPE), can further generalize the model. Importantly, the activation energy for crosslinking of fully cured PV encapsulant products from temperature or UV is presently unknown or unavailable. In this work, we subject EVA, POE, and EPE encapsulants to a set of accelerated aging conditions, varying the temperature, UV intensity, and relative humidity. We use DSC, FTIR, and Soxhlet extraction (gel content) to characterize the encapsulants' changing molecular structure. This allows for determination of the photochemical degradation and crosslinking kinetics of the encapsulants. Preliminary results show an increase in gel content (crosslinking) and a decrease in crystallinity of EVA, POE, and EPE encapsulants under hot-aerobic (90 deg C, 22% RH) and hot-anaerobic (90oC, sealed in N2 air) accelerated aging, even in the absence of UV and crosslinking initiating agents. For a least squares regression with an assumed first-order crosslinking kinetics, the crosslinking rate parameters were computed for the three encapsulants under hot-aerobic and hot-anaerobic aging conditions. FTIR analysis showed insignificant encapsulant degradation for hot-aerobic and hot-anaerobic aging, demonstrating the critical role of UV and moisture in accelerating degradation. Aging conditions with UV exposure and elevated humidity are presently in progress.
Here, this study demonstrates the 100 g scale manufacture of a plutonium alloy that ages at an accelerated rate. The resulting alloy ages six times faster than typical weapons-grade plutonium due to the addition of 238 Pu. As a major innovation, the process involved using a partial direct oxide reduction technique. This method was achieved by developing a new, complex geometry stirrer using additive manufacturing to reduce the 238Pu oxide and efficiently incorporate it into weapons-grade plutonium metal. The material was then purified by molten salt extraction and electrorefining before being alloyed with gallium. The alloy was then cold-rolled and annealed in a homogenization heat treatment. The resulting disk was characterized by metallography and differential scanning calorimetry, and the impurity content was determined using analytical chemistry techniques. The results show that a homogeneous delta phase plutonium alloy was achieved with expected microstructure and minimal impurities. This study was also successful in changing the plutonium isotopic composition by incorporating additional 238 Pu to accelerate the effects of radiation damage. This enables researchers to study long-term aging phenomena in a reduced time frame, thus avoiding the need for large-scale material production and circumventing the limitations of using naturally aged, archived plutonium.
In this study, we highlight some important factors in the specimen preparation methods for evaluating photovoltaic backsheet properties after accelerated aging. Two different sequences are considered: Method (I) cut-then-age: cut into 1-cm wide strips and then expose to stress, and Method (II) age-then-cut: expose a larger sheet to stress and then cut into 1-cm widths for mechanical property measurements. We also compare the effect of three cutting methods, (a) tensile specimen punch, (b) paper cutter, and (c) fresh razor blade. Several commercial backsheets were evaluated, with stress exposures including (a) pressure cooker test (PCT), (b) dry ultraviolet (UV) radiation exposure, and (c) UV combined damp heat tests. Fourier transform infrared spectrometer (FTIR) and intrinsic viscosity (IV) were used to analyze the materials on unstressed materials and samples exposed to PCT. The results show that both the cutting method and the time of cutting have an impact on the backsheet mechanical properties. Additionally, under UV exposure, Method II, age-then-cut, generally resulted in a higher average value, with more variation than Method I; however, if the side strips from Method II were excluded, the variation dropped to the same level. This is because the specimens at the sides of the sheet get additional damage from UV light from the exposed sides of the sample. In contrast to UV exposure, PCT specimens prepared by Method II result in lower average values and higher variability. This is attributed to embrittlement through the bulk of the sample where the cutting of embrittled specimens appears to result in more edge defects which can then initiate a break at smaller strains. The data suggest that for UV exposures, the specimens should be cut after aging and the exposed side specimens discarded, and that for PCT exposures, the specimens should be cut before the exposure.
Epigenetic age acceleration (EAA) is robustly linked with mortality and morbidity. This study examined risk factors of EAA and its association with overall survival (OS), progression-free survival (PFS), and quality of life (QOL) in patients with head and neck cancer (HNC) receiving radiation therapy.
Diffusion limited oxidation (DLO) as a phenomenon has complicated material lifetime predictions from accelerated aging studies. Many methods to analyze DLO have been developed in recent years. However, an analytical tool for high throughput and low-cost analysis of DLO affected samples remains absent from the literature. Color differences in polymers exposed to oxidative conditions have recently been observed and correlated to increased concentrations of oxidation products. Herein, total color difference was utilized to rapidly quantify DLO in ethylene propylene rubber (EPR) polymeric cable insulation specimens. Insulation specimens were aged at 121 °C, 136 °C, 150 °C, and 165 °C and a 10% ?E*ab difference between the specimen edge and specimen center was used as the threshold for DLO. Based on these specifications DLO was observed in EPR insulation specimen at temperatures of 136 °C and above, with an increasing degree of DLO observed as the time of exposure increased. The method presented in this work represents a quantitative and high-throughput method for the investigation of DLO with a low cost barrier for entry.
To understand degradation routes and improve the stability of perovskite solar cells (PSCs), accelerated aging tests are needed. Here, we use elevated temperatures (up to 110°C) to quantify the accelerated degradation of encapsulated CsPbI 3 PSCs under constant illumination. Incorporating a two-dimensional (2D) Cs 2 PbI 2 Cl 2 capping layer between the perovskite active layer and hole-transport layer stabilizes the interface while increasing power conversion efficiency of the all-inorganic PSCs from 14.9 to 17.4%. Devices with this 2D capping layer did not degrade at 35°C and required >2100 hours at 110°C under constant illumination to degrade by 20% of their initial efficiency. Degradation acceleration factors based on the observed Arrhenius temperature dependence predict intrinsic lifetimes of 51,000 ± 7000 hours (>5 years) operating continuously at 35°C.
Additive manufacturing (AM) is a relatively new technological advancement that allows for rapid prototyping, development of intricate shapes, and reduction in manufacturing time. The materials of interest for this project are Ultem 1010, ABS M30, FDM Nylon 12, PC, and PPSF. However, little is known regarding the aging behavior of these AM materials. The limited aging study outlined herein was designed to compare the chemical, physical, and mechanical properties of AM parts as they experience accelerated aging at 70 °C for a total of 24 weeks. In general, ABS M30 stood out as it appeared to undergo chemical and physical changes leading to increase in density and an overall more brittle material, making this commonly used material not attractive for long-term use.
Elucidating aging mechanisms in real-world applications is a critical component for developing and maintaining Cu/SSZ-13 SCR catalysts. To reveal gaps between laboratory accelerated aging and real-world aging, herein we report thorough comparative studies between 6 representative catalysts. Here, we apply a wide range of catalyst characterization methods, including surface area/porosity analysis, X-ray diffraction (XRD), H 2 -temperature programmed reduction, NH3-temperaure programmed desorption, solid-state nuclear magnetic resonance (NMR), in situ X-ray photoelectron (XPS) and electron paramagnetic resonance (EPR) spectroscopies, to gain atomic-level knowledge on Cu transformation under different aging protocols. We then correlate such knowledge to SCR, NH 3 /NO oxidation kinetic behavior of the catalysts. We found that sulfur aging plays the most important role in interpreting catalyst degradation during real-world application, including direct sulfur poisoning of isolated Cu II SCR active species to CuSO 4 -like species, the agglomeration of such species to multinuclear CuSO 4 clusters, and eventually, CuO formation during desulfation treatments. Such chemistries convert SCR active Cu to SCR inert Cu moieties without severely deteriorating catalyst support integrity. These characteristics are partially replicated by hydrothermal aging in the presence of SOx but are poorly mimicked by hydrothermal aging alone.
This study focuses on two separate investigations of the main aging mechanisms: alkali–silica reactivity (ASR) and the corrosion of reinforcing steel (rebar) concrete, both of which may result in a premature failure to meet the serviceability or strength requirements of a concrete structure. However, these processes occur very slowly, spanning decades. The impact of direct chemical additives to fresh concrete to accelerate ASR and the corrosion of reinforcing steel on the fresh and hardened properties of the ensuing material are investigated to inform the potential use of chemicals in large-scale studies. The deterioration of reinforced concrete (RC) is determined by means of expansion, cracking, bulk diffusivity and surface resistivity measurements, and compressive, split tensile and flexural strength tests. The results indicate that the addition of sodium hydroxide and calcium chloride can effectively accelerate the crack formation and propagation in concrete due to ASR and the corrosion of rebar, respectively. The ASR-induced cracks maintained a constant crack width from 0.05 mm to 0.1 mm over the measurement period regardless of the intensity of aging acceleration. Adding 4% chloride by weight of cement for accelerating rebar corrosion resulted in an average crack that was 82% larger than in the case of ASR accelerated with the addition of sodium hydroxide. The addition of alkali resulted in an increase in early-age (7-day) strength. At a total alkali loading of 2.98 kg/m3, 3.84 kg/m3 and 5.57 kg/m3, the 28-day compressive strength of concrete decreased by 3%, 10% and 24%, respectively. Similarly, a higher early-age strength and a lower later-age strength was observed for the concrete in the presence of corrosive calcium chloride. The results from this research are expected to inform future studies on the long-term performance of RC structures under accelerated ASR and corrosion.
In this paper we present measurements and analysis on the mechanical and thermomechanical properties of the LLM-105 based plastic bonded high explosive RX-55-DQ. Specifically we present uni-axial compression, and thermal measurements (CTE and ratchet growth), and for some of the measurements we provide a comparison to measurements on TATB-based PBX 9502. We also present the same mechanical property measurements performed on RX-55-DQ samples that underwent accelerated aging.
During aging in the human mammary gland, luminal epithelial cells lose lineage fidelity by expressing markers normally expressed in myoepithelial cells. We hypothesize that loss of lineage fidelity is a general manifestation of epithelia that are susceptible to cancer initiation. In the present study, we show that histologically normal breast tissue from younger women who are susceptible to breast cancer, as a result of harboring a germline mutation in BRCA1, BRCA2 or PALB2 genes, exhibits hallmarks of accelerated aging. These include proportionately increased luminal epithelial cells that acquired myoepithelial markers, decreased proportions of myoepithelial cells and a basal differentiation bias or failure of differentiation of cKit + progenitors. High-risk luminal and myoepithelial cells are transcriptionally enriched for genes of the opposite lineage, inflammatory- and cancer-related pathways. We have identified breast-aging hallmarks that reflect a convergent biology of cancer susceptibility, regardless of the specific underlying genetic or age-dependent risk or the associated breast cancer subtype.
PV cables allow the collection and distribution of electricity from modules to the energy grid. Durable cabling allows continuous operation of PV installations. Cables with a life less than that of the modules must be replaced - reducing electricity generation and adding to the system operating expense. We have examined the durability of a variety of representative cable samples using artificial UV weathering (IEC TS 62788-7-2) and combined accelerated stress testing (C-AST). Jackets in this study include PV-rated (polyolefin), building wire (PVC/PA), and multi-conductor (rubber, as in PV trackers), with some examples of black and red cables. Characterizations at read points include appearance (camera and optical microscope), surface roughness (linear profilometry), instrumented indentation, surface morphology (SEM), chemical composition (EDS), thermal decomposition (TGA), phase transition (DSC), crystalline structure (WAXS), and polymer chemical structure (FTIR). Complimentary examinations confirm damage to the external and interior layer(s) of less durable samples, including changes in morphology (e.g., cracking), chemistry (e.g., oxidation), structure, and mechanical performance (e.g., through-thickness modulus and hardness). The results may be generally compared to other examples from the field (PV installations) or after accelerated testing (IEC 61215). The methods in this study are presently being applied in a follow-on C-AST study, incorporating both dynamic and kinematic fixtures.