Thermal Aging Research Articles

Rational Tailored Polyfluorosubstituted Amide Molecule for Stabilizing PbI6 Framework and Inhibiting Ion Migration Toward Highly Efficient and Stable Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs), while highly efficient, face stability challenges that hinder their commercial application. These instability issues mainly arise from the fragile nature of Pb─I bonds in perovskites, which easily break under environmental stresses such as heat and light, leading to the breakdown of the [PbI6] framework and irreversible degradation. To address these issues, a multifunctional molecule, N1,N4‐bis(2,3,5,6‐tetrafluoro‐4‐iodophenyl)terephthalamide (FIPh‐A), is designed and synthesized to enhance the stability of perovskite films and devices. FIPh‐A molecule possesses carbonyl, amino, and iodotetrafluorophenyl groups that bind and stabilize Pb2+ ions and [PbI6]4− octahedra structure, preventing ion migration in perovskite films. The activation energy of ion migration increases obviously from 0.28 eV to 0.39 eV by adding FIPh‐A verified by experiment results. The residual strain is also released efficiently by introducing FIPh‐A molecule into perovskite films characterized by grazing incidence X‐ray diffraction. The champion PSC with FIPh‐A achieves a power conversion efficiency of 24.60%. After 500 h of continuous illumination (ISOS‐L‐1) and 300 h of thermal aging at 80 °C (ISOS‐D‐2I), these PSCs with FIPh‐A maintained 93% and 77% of their initial efficiency, respectively. These results emphasize the potential of multifunctional additives in overcoming the stability challenges of PSCs, thereby facilitating their commercial advancement.

Comparative characteristics of thermal stability of polyethylene in the presence of complex fillers based on natural raw materials

A comparative analysis of the effect of new complex fillers of natural origin on the process of thermal aging of high-pressure polyethylene is carried out. During the research, it was found that the studied fillers have a stabilizing effect, inhibiting the processes of thermal oxidation of high-pressure polyethylene. The stabilizing effect of fillers is due to the presence in their composition of metal oxides capable of chemical interaction with oxygen-containing groups in oxidized polyethylene. It has been established that the carbon-mineral filler has a higher thermostabilizing effect than the carbon-silicon filler from carbonized rice husk.

Lifetime prediction of EPDM sealing materials with thermal aging under constant compression

Abstract EPDM (Ethylene Propylene Diene Monomer) is an important engineering sealing material. Thermal aging leads to a decline in its service life. In this study, the static sealing lifetime of EPDM sealing materials is investigated by thermal aging experiments under constant compression. Based on the variation pattern of compression set over aging time at different aging temperatures (80 °C, 100 °C, and 120 °C), a lifetime prediction model for EPDM sealing materials is derived using chemical reaction kinetics and the Arrhenius equation. The model is compared with the experimental results. The results show that the prediction model is highly reliable. The theoretical life of EPDM after thermal aging at 25 °C is 30.6 years, 53.1 years, and 89.1 years, respectively, when the compression set is 40%, 45%, and 50 %.

Fracture Resistance of Space Maintainers Produced Using 3D Printable Materials.

This study aimed to evaluate the fracture resistance of space maintainers (SMs) produced using 3D-printable materials (metal, resin and polyetheretherketone [PEEK]) after thermal aging and compare them with conventional space maintainers. A standardised typodont model for paediatric dentistry was utilised, and band and loop space maintainers were designed digitally using computer-aided design (CAD) technology. Four groups were established: Conventional, 3D printed metal, 3D printed resin, and 3D printed PEEK. Fracture resistance was assessed after 10,000 thermal cycles, simulating oral conditions. Fracture tests were conducted using a universal testing machine, applying vertical force to the band and loop junction until fracture. Statistical analyses were performed using one-way ANOVA and the Tukey HSD test (P<0.05). Although the fracture resistance values showed that metal, resin, and PEEK 3D printed band and loop space maintainers can be acceptable clinically, the permanent resin may be preferable to printable material because of their aesthetic properties.

The Evolution of Interfacial Intermetallic Compound Growth and Solder Joint Strength of Sn-40Pb/Cu under Thermal Aging

The Evolution of Interfacial Intermetallic Compound Growth and Solder Joint Strength of Sn-40Pb/Cu under Thermal Aging

Analysis of noise and its characteristics in avalanche photodiode

Avalanche photodiodes (APDs) produce noise during operation, which affects the device performance. However, the previous research on its noise is mainly theoretical analysis and is only reflected as optical noise. Therefore, according to the characteristics of APD material and the mechanism of noise generation, the main noise of the device is analyzed in this paper. First, the test method of noise in APDs is established, including testing of dark noise, optical noise, and multiplication noise in high frequency bands. The main noises in APDs are 1/f noise, thermal noise, shot noise, generation recombination noise, and multiplication shot noise, and shot noise is suppressed by Fermi–Dirac distribution and Coulomb action. Second, the reliability of APDs is evaluated by measuring and analyzing the noise parameters of the device through thermal aging experiments. It is concluded that the defects introduced by thermal aging can be reflected by the change in noise, which is consistent with the results in the literature. This method can comprehensively obtain the noise in APDs, which is helpful to improve the working efficiency, life, and reliability of the device.

Advancing Thermal Stability in Natural Ester Oil-Paper Insulation Systems via Precision Nanostructuring with Parylene Films: Experimental and Molecular-Level Comprehensive Assessment

The oil-paper insulation system in eco-friendly fire-retardant transformers depends on hydrophilic natural ester insulating oil. Moisture within the system synergistically interacts with aging, worsening oil-paper insulation degradation and hastening overall system aging. Chemical vapor deposition was used to create parylene surface-modified insulating paper as a strategy to inhibit moisture-induced aging in natural ester oil-paper insulation. The effectiveness of the approach was identified by a comprehensive assessment of the physicochemical and electrical properties of the parylene surface-modified insulating paper. The findings from accelerated thermal aging at 130 °C for 90 days on the natural ester oil-paper insulation system reveal the outstanding lipophilic and hydrophobic properties while maintaining electrical characteristics of the parylene surface-modified insulating paper. After 90 days of aging, the parylene surface-modified insulating paper exhibited a 56.76% higher degree of polymerization and a 19.36% significantly lower moisture content than conventional cellulose insulating paper. In the natural ester oil-paper insulation system, the parylene surface-modified insulating paper led to a notable 63% reduction in insulating oil acid value, a 60.50% decrease in dielectric loss, and a substantial 20.35% increase in AC breakdown voltage. Molecular-level investigations revealed the inhibitory mechanism of the parylene film, offering a promising solution to enhance the thermal stability and aging resistance of natural ester oil-paper insulation systems.

Long-term thermal aging effects in ferritic-martensitic steel HT9

The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M23C6, HCP and FCC MX phase and Laves M2X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.

Unexpected thermal aging effect on brittle fracture and elemental segregation in modern dissimilar metal weld

A full-scale dissimilar metal weld safe-end mock-up, precisely replicating a critical component of a modern nuclear power plant, was investigated. The brittle fracture behavior, carbide evolution and nanoscale elemental segregation in the heat-affected zone (HAZ) of low alloy steel (LAS) were analyzed under both post-weld heat-treated and thermally-aged conditions (400 °C for 15,000 h, equivalent to 90 years of operation) using analytical electron microscopy and atom probe tomography. The observed increase in grain boundary (GB) decohesion and intergranular cracking on the fracture surface and the decrease of fracture toughness are primarily attributed to P and Mn segregation to GBs and the coarsening of carbides upon long-term thermal aging. The direct observations of significant elemental segregation to GBs and the consequent reduction in fracture toughness in the HAZ are unexpected for modern low-phosphorus LASs, highlighting potential concerns for evaluating the structural integrity of modern nuclear power plants.

Microstructure and shear properties of interconnect interface between multi-phase heterogeneous SnBi eutectic alloy and Cu substrate

The microstructures of the interconnect interfaces between Sn58Bi eutectic alloy and Sn53Bi3Cu3Zn2Ag2Sb multiphase alloy and Cu substrate, as well as the strength of the interconnect joints were systematically studied after 1008 h thermal aging at 70℃. Compared with the unmodified Sn58Bi alloy, the addition of alloying elements inhibited the coarsening of the organization and the growth of intermetallic compound (IMC) at the interconnect interface. At the same time, the Cu3(Sn, Zn) phase in the upper part of the IMC and twinned Cu in the substrate can contribute to enhanced the mechanical properties of the interconnect joints. Compared to their respective shear strengths after reflow, the strength of the modified Sn53Bi3Cu3Zn2Ag2Sb/Cu interconnect joints increased by 22.3 %, while the strength of the Sn58Bi/Cu interconnect joints decreased by 18.3 % after thermal aging. This study indicate that alloying modification can effectively improve the shear strength of interconnect joints during aging, thus improving interconnect reliability.

Microstructural Dependence of the Impact Toughness of TP316H Stainless Steel Exposed to Thermal Aging and Room-Temperature Electrolytic Hydrogenation.

This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

Study on the hydration characteristics, mechanical properties, and microstructure of thermally activated low-carbon recycled cement

Based on the thermal activation method, utilizing fine particles of waste concrete to prepare low-carbon recycled cement (RC) is currently one of the research hotspots. Based on existing literature research results, this paper identifies four calcination temperature conditions (120, 450, 750, 1000 ℃) and uses replacement rates of 10 %, 30 %, 50 %, 70 %, and 100 % of RC to replace ordinary Portland cement (OPC).The main physical properties, hydration characteristics, mechanical properties, and microstructure of RC are studied. The study elucidated the influence of RC thermal activation temperature, replacement rate, fineness, and age on its hydration characteristics, mechanical properties, and microstructure, establishing a macro-micro correlation for RC and revealing the mechanism of improvement in mechanical properties of thermal-activated RC. The research indicates that in the initial stage of hydration, RC exhibits a relatively fast hydration rate, with higher initial total heat release than OPC. Hydration products include internal hydration products (formation of C-(A)-S-H gel) and external hydration products (formation of plate-shaped AFm). Furthermore, RC exhibits a faster hydration rate at a hot activation temperature of 750°C, with CH and C-S-H gel transforming into the highly hydrated α´L-C2S, forming a denser microstructure at an early stage. Moreover, at a replacement rate of 30 %, the compressive strength of cement mortar reaches its optimum at 28 days, achieving 13.81 MPa, equivalent to 60.7 % of OPC cement mortar, with a 66.67 % reduction in carbon emissions. Microstructure analysis reveals that when the temperature reaches 1000°C, excessive combustion of RC leads to the formation of low-reactivity C2AS and β-C2S, resulting in a decrease in macroscopic mechanical properties. Additionally, increasing the fineness of RC significantly enhances its rehydration capability, especially as the age increases. This study is of great significance for the preparation of green cement-based composite cementitious materials.

Magnetic Indicator for Evaluating Cu Clustering and Hardening Effect in RPV Model Alloy

The reactor pressure vessel (RPV) is a critical barrier in nuclear power plants, but its embrittlement during service poses a significant safety challenge. This study investigated the effects of Cu-enriched clusters on the mechanical and magnetic properties of Fe-0.9 wt.%Cu model alloys through thermal aging. Using Vickers hardness tests, Magnetic Barkhausen Noise (MBN) detection, and Atom Probe Tomography (APT), the study aimed to establish a quantitative correlation between MBN signals, Vickers hardness, and Cu-enriched clusters, facilitating the non-destructive testing of RPV embrittlement. Experimental results showed that the hardness and MBN parameters (RMS and Vpp values) changed significantly with aging time. The hardness increased rapidly in the early stage (under-aged), followed by a plateau and then a decreasing trend (over-aged). In contrast, MBN parameters decreased initially and then increased. APT analysis revealed that Cu-enriched clusters increase in size to 4.60 nm and coalesced during aging, with their number density peaking to 3.76 × 1023 m−3 before declining. An inverse linear correlation was found between MBN signals and the combined factor Nd2Rg (product of the number density squared and the mean radius of Cu-enriched clusters). This correlation was consistent across both under-aged and over-aged states, suggesting that MBN signals can serve as applicable indicators for the non-destructive evaluation of RPV steel embrittlement.

Repair strength of 3D-printed denture base resins: Effect of surface treatment and repair material type.

The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D-printed denture base resins after thermal aging. Bar-shape specimens (64×10×3.3mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles-abrasion, or (3) both methods (aluminum oxide particles-abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3-point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p<0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p<0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p>0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p<0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto-polymerized resin (p<0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto-polymerized while cohesive and mixed were dominant with composite repair groups. Surface treatment improved the repair strength of 3D-printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D-printed denture base repair.

Effect of Different Liquids and Thermal Aging Procedures on the Shear Bond Strength of APC II, APC Flash-Free, and Conventional Ceramic Brackets: An In Vitro Study.

The purpose of this study was to compare the effects of cherry juice, coffee, coke, gastric acid, and the thermo-aging procedure (TAP) on the shear bond strength (SBS) of APC II, APC flash-free, and conventional ceramic brackets. A total of 180 human premolar teeth were randomly divided into three major groups according to the type of ceramic bracket. Then, six subgroups (n=10) were established from each major group: Group 1: control; Group 2: only TAP; Group 3: 72 hours of cherry juice exposure + TAP; Group 4: 72 hours of coffee exposure + TAP; Group 5: 72 hours of coke exposure + TAP; and Group 6: 24 hours gastric acid exposure + TAP. SBS was assessed for each specimen using a universal test device, and the adhesive remnant index (ARI) was scored under a light microscope. Kruskal-Wallis and post-hoc Tamhane tests were used to analyze the data. Among the control groups, the highest SBS value belonged to conventional ceramic brackets (p<0.01). SBS values for all groups decreased as a result of each liquid and TAP. Gastric acid and coke had the greatest detrimental effects on SBS, while TAP had the least negative effects. The SBS values of APC II, APC flash-free, and conventional brackets were found to be statistically insignificant after different liquid exposures and TAP. TAP and various fluids had a negative impact on the SBS value of ceramic brackets. SBS values, however, were still higher than clinically acceptable (8-9 MPa) values, even after exposure to gastric acid and coke.

Innovative Thin PiG Plates Boost the Luminous Efficacy and Reliability of WLEDs for Vehicles

In this study, we demonstrate the high luminous efficacy of 118 lm/W and the high reliability of white LEDs (WLEDs) through 450 °C thermal aging, utilizing four-inch YAG: Ce3+ phosphor-in-glass (PiG) plates designed for vehicle headlights. The sintering process of mixing glass and phosphor typically generates pores, which can scatter light and reduce the luminous efficacy of the fabricated PiG. In this study, we produced four-inch PiG plates under four different fabrication conditions to evaluate their luminous efficacy. Our results revealed that the PiG plate with a thin thickness of 0.08 mm exhibited a 16.83% increase in luminous efficacy compared to the 0.15 mm plate, attributed to reduced light interaction with the pores. Unlike silicone-based phosphor WLEDs, which offer high performance but lower reliability due to the silicone resin’s low transition temperature (150 °C), our novel thin PiG plate achieves high performance and reliability. This advancement suggests that the proposed thin PiG plate could replace traditional silicone-based phosphors, enabling the development of high-quality WLEDs for vehicle headlights in automotive applications.

Ferritic–Martensitic Steels in Power Industry: Microstructure, Degradation Mechanism, and Strengthening Methods

Ferritic–martensitic (F–M) steels are widely used for high‐temperature pressure vessels and reactor cladding structures in power plants. The high operating temperatures and pressures, as well as the radiation environment, significantly challenge the mechanical stability of these steels. Here, the degradation mechanisms in F–M steels during creep and thermal aging under these harsh environments are reviewed. The exceptional mechanical properties of F–M steels are mainly attributed to their well‐constructed microstructures and chemical compositions. Microstructural barriers such as dislocations, solid solution atoms, and precipitates play key roles in resisting degradation. During the long‐term service, the microstructures undergo gradual evolution, resulting in a deterioration of mechanical properties at the macrolevel. In addition to the degradation mechanisms, some recent advancements in strengthening methods, including microalloying strengthening, thermomechanical treatment (TMT), and oxide dispersion strengthening, are summarized, aimed at the development of next‐generation F–M steels. The strengthening of the F–M steels is mainly achieved by enhancing the thermal stability of their microstructures. Insight into both the deterioration mechanisms and strengthening methods of F–M steels may pave the way for new approaches in developing high‐performance steels for applications in next‐generation power plants operating at ultrahigh operating temperatures and pressures.

Ages and structural relationships in the Ganderian central Cape Breton Highlands, Nova Scotia, Canada

Structural complexity of the Cape Breton Highlands is a key problem in reconstructing tectonic events in the northern Appalachian orogen. A new U–Pb thermal ionization mass spectrometry age of 428.53 ± 0.16 Ma for metarhyolite in the Calumruadh Brook Formation shows that volcanic and sedimentary rocks were deposited before collision of the Aspy and Bras d'Or terranes along the Eastern Highlands shear zone. A new U–Pb laser ablation zircon age of 394 +6/−4 Ma confirms that peak metamorphism in the Middle River complex continued during convergence linked to late stages of the Acadian orogeny. The compressive tectonic environment evolved into a transpressional system after initial collision in the late Silurian and caused a repeated pattern of imbrication of units in the Aspy terrane in the hanging wall in the collision. The shear zones bounding the geological units are curvilinear and have south-directed kinematics, imbricating units and transporting higher grade rocks over lower grade rocks, and moving plutons upward relative to their host rocks during and shortly after intrusion. The vergence of imbrication is parallel to the direction of transpressional movement on the main Eastern Highlands shear zone. This geometry is present in Ordovician–Silurian rocks and repeated in Devonian plutonic rocks, indicating that the overall transpressional tectonic setting was a long-lived feature of the orogen. The shear zones localized late syn- to post-deformational plutons that intruded at ca. 375–370 Ma. By the latest Devonian, emplacement of the ca. 363 Ma Margaree and related plutons marked the beginning of extension in the central Cape Breton Highlands.

Electrical breakdown mechanism and life prediction of thermal-aged epoxy/glass fibre composites

Epoxy/glass fibre composites possess excellent mechanical and electrical properties and are widely utilised in electrical and electronic power equipment. However, the composites exhibit relatively poor thermal conductivity, causing the temperature of the composites to increase during the operation of power equipment, resulting in a significant reduction in the electrical breakdown strength. Although the effects of thermal aging on polymeric materials have been widely studied, its influence on electrical strength mechanisms has not been investigated at the molecular level. In this study, epoxy/glass fibre composite specimens were subjected to accelerated thermal aging treatment for 360 h at 180 °C. Functional groups, molecular chain dynamics, and electrical breakdown are characterised using infrared spectroscopy, dielectric spectroscopy, and breakdown measurement. Subsequently, electrical breakdown mechanism and life prediction of the thermally aged composites are discussed. During thermal aging, the epoxy resin molecular chains undergo continuous oxidation and chain scission, which generate numerous polar functional groups and short chains and an increase in the free volume. This triggers an enhancement in the chain segmental dynamics, thereby significantly reducing the activation energy of the epoxy resin. After 360 h, activation energy decreased from 0.78 eV to 0.67 eV. The DC breakdown voltages of the specimens decreased from 168.28 kV/mm to 134.91 kV/mm. An insulation life prediction model for thermally aged epoxy/glass fibre composites is established based on the time-temperature equivalence theory. The prediction results indicate that the service life of the operational composites is approximately 11.2 years at 353 K, which is consistent with engineering experience.

Characterization of temperature regulating, high-temperature rheological and anti-aging properties of asphalt mastic modified with SSPCMs

The objective of this study is to explore the potential of utilizing self-developed SSPCMs as additives for heat storage temperature regulation in asphalt mastic modification. To achieve this aim, a variety of asphalt mastics with different F-A volume ratios and SSPCM contents were formulated, and their high-temperature rheological properties, modification mechanisms, thermoregulation capabilities, and aging resistance performances were analyzed. The results of temperature regulation test indicated that the maximum cooling amplitude of asphalt mastic could reach 11.3°C, showing a great promising application for cooling asphalt pavements. Additionally, the incorporation of SSPCMs generally resulted in positive impacts on both the high-temperature rheological properties and temperature sensitivity of the asphalt mastics. Moreover, the aging indices GAI, ICO and ISO of the modified asphalt mastic with 30 % SSPCMs decreased by 5.6 %, 18.3 % and 8.7 %, respectively, compared with control asphalt mastic, implying that the incorporation of SSPCMs can retard the aging process of asphalt and enhance the thermal oxidative aging resistance of the asphalt mastics. In summary, the current study demonstrates the feasibility, improved performance, and effective thermoregulation properties of SSPCMs in asphalt mastics.