Room Temperature Aging Research Articles

Formation of orthorhombic CH3NH3PbI3 perovskite co-doped with ytterbium and gadolinium

Orthorhombic CH3NH3PbI3 perovskite crystals were formed by co-doping1.0 at% ytterbium and 0.5 at% gadolinium at lead sites. X-ray diffraction results showed that the perovskite crystals fabricated at 190°C in an atmospheric air provided an orthorhombic structure even at room temperature. Although the highest power conversion efficiency was 1.73 % for the as-prepared device, the efficiency was improved to 11.6 % after 113 days, which could be due to decrease in series resistance caused by (100)-oriented crystal growth during room temperature aging.

Atomistic Modelling of [formula omitted]-Fe2C Formation During Low-Temperature Tempering of Martensitic Carbon Steel

The control of carbide formation is crucial for the development of advanced steels. One of the more stable carbides occurring at room temperature ageing of martensite is η-Fe2C. In this work, we study structural transformations which occur during low-temperature ageing in Fe-C martensite using computer modelling based on the atomic density field method. It is shown that homogeneous bct solid solution with 2at.% of C undergoes bct →η-Fe2C transformation. An important result is that the ordering Fe2C structure may be considered a deformed rutile structure. In addition, the link between η-carbide and other meta-stable carbides is discussed based on the Fe2n+1Cn (n=1,2,3,…) Magnéli phases. The Magnéli phases comprise a sequence of carbon-rich 110α′ layers with different periods to accommodate the loss in stoichiometry. The simulated microstructure is compared to experimental data found in the literature.

Cobalt nanoparticles confined nitrogen–doped carbon integrated bimetallic Co2P–VP heterostructured composite: A MOF integrated 3D arrays for catalytic water splitting

A robust electrode material with outstanding stability at high current density is crucial for the practical application of water splitting. We present an intertwined heterostructure composed of in-situ confined cobalt nanoparticles (Conp) in nitrogen-doped carbon (N–C), derived from functionalized zeolitic imidazolate framework–67 (ZIF−67), and composited with the hetero phase bimetallic cobalt vanadium phosphide (Co2P−VP) through a hydrothermal reaction, room temperature aging, and chemical vapor deposition (CVD) for simultaneous phosphidation, graphitization, and reduction. The synergistic effect generated across the multiple heterointerfaces of Co2P, VP, and Conp in the N−doped carbon on nickel foam, as the Co2P–VP@N–C/Co heterostructure, exhibits outstanding electrocatalytic performance for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrochemical water splitting. The Co2P–VP@N–C/Co (+,−) alkaline electrolyzer demonstrates a low potential of 1.49 and 1.71 V to achieve current densities of 10 and 100 mA cm−2, respectively. It exhibits outstanding stability during continuous operation for 100 h at 100 mA cm−2, with 98.02 % retention. The outstanding performance is credited to the synergistic interaction and d-electronic modulation of the metallic hetero phasic Co2P–VP moiety and confined Conp in a functionalized N−doped porous carbonaceous heterostructure. Density Functional Theory (DFT) validates the regulation of electronic structure for efficient redistribution of local charges and electron transfer.

Research on fatigue performance of “sandwich metal-structured ” composite materials in ultra-low temperature environments

The aim is to investigate the influence of aluminum content in the FeCoCrNiAlx series high-entropy alloys, different aluminum alloy damping layers, and the thickness of damping layers on the fatigue performance of sandwich structure composite material plates after room temperature and low-temperature aging treatment. By using abaqus/fe-safe simulation, as well as liquid nitrogen low-temperature aging treatment and fatigue tensile testing, the differences in fatigue performance between composite materials treated with low-temperature aging and those untreated at room temperature were observed. The increase in aluminum content significantly improves the lifespan of the composite materials, and after low-temperature aging treatment, the change in strength is even more pronounced. Keeping the thickness and material of the upper and lower layers constant, the tensile life of the material, both untreated and treated at low temperatures, shows a significant increasing trend as the thickness of the middle damping layer increases. Other conditions being equal, the iMPact of different damping layer aluminum alloys on fatigue performance is also very evident. In terms of tensile cycles, the ranking is as follows: 7075 > 2A12 > 6061. After low-temperature treatment, the fatigue tension cycles of the 2A12, 6061, and 7075 damping layers under a force of 100 N are respectively 8.66, 7.43, and 2.01 times those of the untreated composite materials.

How does room temperature cycling ageing affect lithium-ion battery behaviors under extreme indentation?

Safety of lithium-ion battery (LIB) cells throughout the whole lifecycle has drawn enormous research interest. Understanding how cycling ageing affects the mechanical-electrical-thermal responses of LIB cells under mechanical abuse is meaningful for more considerate safety design. In the present study, impact of room temperature ageing on morphology of lithium-ion pouch cell was experimentally explored at first, which clearly identified the deposition phenomenon on electrodes induced by electrolyte consumption. Spherical indentation along out-of-plane direction was carried out on both pristine and aged cells, in which the mechanical-electrical-thermal responses were all monitored. Test results indicate that the mechanical response of the aged cells is quite distinct from the pristine ones, characterized by a rightward shift of the force-displacement curve. Electrical and thermal responses of the aged cells were comparatively less severe. It is inferred that those deposits generated during the ageing process postpone the failure of cells. The short circuit of aged cells behaves relatively tenderly as short contact is alleviated by deposits on the surface of electrodes. By combining the present results with previous researches, correlation between the ageing mechanism and the mechanical abuse failure was sorted for different cells subjected to different ageing processes. It is recognized that changes in mechanical, electrical, and thermal responses of aged cells are highly dependent on both ageing condition and battery configuration.

Effect of temperature aging of thermoset UD prepregs on inter‐ply friction behavior and formability in prepreg compression molding process

AbstractLimited material out‐life of thermoset prepregs is unavoidable attributed to the slow crosslinking reaction between molecules and curing agents. Previous studies have explored the effects of temperature aging on the final mechanical properties of composites, but have been limited by the processing mismatch in compression molding. The research primarily focuses on the effects of forming temperature and ply angle of prepreg on inter‐ply friction behavior at various aging levels. The importance of inter‐ply friction on the forming quality is further discussed through the L‐shaped specimens forming with prepreg compression molding (PCM) process. Firstly, a comprehensive influence of aging on the properties of resin including cure kinetics, gel point, glass transition temperature (Tg) and viscosity of UD prepreg are characterized and discussed. And then, the influence of factors including resin aging, forming temperature and prepreg ply orientation on the inter‐ply friction are discussed. It can be found that the aging of prepreg reduce 26.47% of inter‐ply friction resistance under room temperature, and the increase of temperature can reduce inter‐ply friction resistance by 79.31%. Finally, the effect of aging on the forming quality is researched by PCM formed L‐shaped components. Results indicated that fresh prepreg with 20°C and prepreg with an aging level of 0.4 performed at 95°C exhibited poor formability, while prepreg with aging level of 0.2 at 95°C exhibited the best forming property. In general, this study provides a basic explain and a practical suggestion to the reuse of room temperature aging thermoset prepregs in PCM process.Highlights A comprehensive of basic properties of aged resin were characterized, as the basic principle for inter‐ply friction behavior analysis. The gel point and final mechanical properties of prepreg were tested, for judging the aged materials whether could be used continuously. The inter‐ply friction behaviors of aged prepregs under various forming temperatures were investigated. The influence of layup orientations on the inter‐ply frictional performance with various aging levels were explored. The effect of aging and forming temperature on the PCM formability were studied and a practical suggestion to the reuse of aged thermoset prepregs in PCM process was given.

Room Temperature Aging of Autotempered Fe–C Martensite

Room Temperature Aging of Autotempered Fe–C Martensite

Manganese-Doped Bimetallic (Co,Ni)2P Integrated CoP in N,S Co-Doped Carbon: Unveiling a Compatible Hybrid Electrocatalyst for Overall Water Splitting.

Rational design of highly efficient noble-metal-unbound electrodes for hydrogen and oxygen production at increased current density is crucial for robust water-splitting. A facile hydrothermal and room-temperature aging method is presented, followed by chemical vapor deposition (CVD), to create a self-sacrificed hybrid heterostructure electrocatalyst. This hybrid material, (Mn-(Co,Ni)2P/CoP/(N,S)-C), comprises manganese-doped cobalt nickel phosphide (Mn-(Co,Ni)2P) nanofeathers and cobalt phosphide (CoP) nanocubes embedded in a nitrogen and sulfur co-doped carbon matrix (N,S)-C on nickel foam. The catalyst exhibits excellent performance in both the hydrogen evolution reaction (HER; η10 = 61mV) and oxygen evolution reaction (OER; η10 = 213mV) due to abundant active sites, high porosity, and enhanced hetero-interface interaction between Mn-(Co2P-Ni2P) CoP, and (N,S)-C supported by significant synergistic effects observed among different phases through density functional theory (DFT) calculations. Impressively, (Mn-(Co,Ni)2P/CoP/(N,S)-C (+,-) shows an extra low cell voltage of 1.49 V@10mA cm-2. Moreover, the catalyst exhibits remarkable stability at 100 and 300mA cm-2 when operating as a single stack cell electrolyzer. The superior electrochemical activity is attributed to the enhanced electrode-electrolyte interface among the multiple phases of the hybrid structure.

Effects of ethylammonium and rubidium addition to guanidinium-based CH3NH3PbI3 perovskite photovoltaic devices prepared at 190 °C in ambient air

Effects of the addition of rubidium (Rb) and ethylammonium (CH3CH2NH3, EA) to guanidinium [C(NH2)3, GA]-based CH3NH3PbI3 perovskite solar cells were investigated. Lattice constants and the (100)-orientation of EA- and Rb-modified perovskite crystals increased compared with those of as-prepared perovskite. Abnormal increases of lattice constants of the GA- and EA-modified perovskite crystals prepared at 190 °C for 10 min in ambient air were also observed during the room temperature aging, which was due to crystal growth of the perovskites, and these features contributed to increased conversion efficiencies of devices based on the modified perovskites. Addition of GA and EA also effectively improved the photovoltaic properties of the device under indoor light conditions using white light-emitting diodes. First-principles calculations of the density of states and band structures indicated a reduction of the total energy through the addition of Rb or EA, suggesting that the current density was improved by the reduced band gap.

A novel methodology to estimate hydrogen diffusivity and its applications in revealing hydrogen effects in CoCrNi medium-entropy alloy versus 316L stainless steel

Hydrogen diffusivity is one of the important factors affecting the susceptibility to hydrogen embrittlement of metals and alloys. Here, we proposed a novel approach to estimate hydrogen diffusivity in FCC alloys by performing nanoindentation experiments with continuous stiffness measurement. In consideration of the plastic zone size around the indentation, the relationship between hydrogen-induced hardness change and the depth from the sample surface was established for two typical FCC alloys—316L stainless steel (SS) and CoCrNi medium-entropy alloy (MEA)—subjected to hydrogen-charging and subsequent room-temperature aging. By combining with the estimation of the through-thickness distribution of hydrogen concentration, hydrogen diffusivity values were successfully determined, which agreed well with the literature data. It was revealed that CoCrNi MEA exhibited a hydrogen diffusivity ∼0.68 times higher than that in SS316L, and that hydrogen-induced softening upon long-term aging (at room temperature) was observed in CoCrNi but not in SS316L. The underlying mechanisms for the distinct hydrogen-related phenomena in CoCrNi MEA were elucidated based on the density functional theory calculations of hydrogen solution energy and vacancy formation energy.

Mechanical properties degradation of Sn 37Pb solder joints caused by interfacial microstructure evolution under cryogenic temperature storage

The interfacial microstructure, shear property and fracture behaviors of Sn37Pb joints after cryogenic temperature storage for different durations were investigated in this study, storage test at room temperature (298 K) and thermal aging test at 423 K were also carried out as comparison. The morphology of interfacial Cu6Sn5 IMCs for the joints stored under 77 K and 173 K transformed from scallop-like to column-like, moreover, the IMC layer thickness slowly increased with prolonged storage time. The growth rate of Cu6Sn5 layer in Sn37Pb joint stored at 77 K was slightly faster as compared with that stored at 173 K. However, the morphology and thickness of Cu6Sn5 IMC layer still remained roughly unchanged after storage at 298 K for up to 40 days. The Cu6Sn5 IMC growth of Sn37Pb joint stored at 77 K and 173 K was expected to be caused by Cu atom diffusion from Cu pad towards Sn37Pb solder, which was induced by the stress gradient. Additionally, the shear force declined and fracture position changed from in Sn37Pb solder to primarily in Sn37Pb solder and partly along the interface with the prolonging of storage time at 77 K and 173 K, which were induced by IMC layer growth.

Artifact-Free Microstructures in the Interfacial Reaction between Eutectic In-48Sn and Cu Using Ion Milling.

Eutectic In-48Sn was considered a promising candidate for low-temperature solder due to its low melting point and excellent mechanical properties. Both Cu2(In,Sn) and Cu(In,Sn)2 formation were observed at the In-48Sn/Cu interface after 160 °C soldering. However, traditional mechanical polishing produces many defects at the In-48Sn/Cu interface, which may affect the accuracy of interfacial reaction investigations. In this study, cryogenic broad Ar+ beam ion milling was used to investigate the interfacial reaction between In-48Sn and Cu during soldering. The phase Cu6(Sn,In)5 was confirmed as the only intermetallic compound formed during 150 °C soldering, while Cu(In,Sn)2 formation was proven to be caused by room-temperature aging after soldering. Both the Cu6(Sn,In)5 and Cu(In,Sn)2 phases were confirmed by EPMA quantitative analysis and TEM selected area electron diffraction. The microstructure evolution and growth mechanism of Cu6(Sn,In)5 during soldering were proposed. In addition, the Young's modulus and hardness of Cu6(Sn,In)5 were determined to be 119.04 ± 3.94 GPa and 6.28 ± 0.13 GPa, respectively, suggesting that the doping of In in Cu6(Sn,In)5 has almost no effect on Young's modulus and hardness.

Superconductivity of Electrodeposited Sn Films

Tin (Sn) films are electrodeposited on Au seed layers for the investigation of superconductivity. The effects of the presence of suppressing additives in electrolyte, the thickness of Sn films, and the room temperature aging of deposited Sn films on the superconducting transition behavior are systematically studied. In addition, the crystallographic structure of electrodeposited Sn and its evolution along with aging time are characterized and are discussed in conjunction with the superconductivity behavior. The current work represents an important step towards the processing of technologically viable superconducting devices.

Sustainable recycling of polyethylene waste through utilization in asphalt paving applications

One the enormous amount of waste polyethylene (PE) materials amassing in Iraq is posing an expensive landfill and disposal issue. The current study examines the potential for employing PE as a partial replacement for environmentally friendly pavement construction. Different amounts of PE were used to partially replace asphalt cement (3 %, 6 %, 9 %, and 12 % by weight). The PE-substituted asphalt (PESA) binders were subjected to the rheological and compatibility properties. Additionally, two asphalt concrete (AC) mixtures-one control and one PEAC-were created for the mechanical and durability experiments. Among the parameters assessed during the tests are the following: adhesion to a variety of substrates and substrate surfaces; elongation at room temperature (aging index); flexibility at elevated temperatures (cracking index); temperature susceptibility; compatibility; and the extensional viscosity of the PESA binder as well as the extensional viscosity of the PESA-mixture (PESAM). Furthermore, the mechanical and durability properties of AC and PEAC mixes were examined using the Marshall stability, Marshall quotient, static indirect tensile strength at 25 and 60°C, tensile strength ratio, and resilient modulus 25°C tests. Results show that PESA binder outperforms virgin asphalt binder in terms of cracking and temperature resistance. PEAC mixture exhibits higher stability, indirect tensile strength, moisture resistance and resilient modulus than AC mixture. According to standard and durability testing, replacing virgin binder with six percent PE can be recyclable and suitable for use as sustainable material for paving applications.

Hardness increases due to (Fe, Cr)2C carbide precipitated during natural aging in high chromium cast iron

The effect of natural aging on the microstructure of carbides and martensite in high chromium cast iron subjected to a destabilizing heat treatment was investigated by correlative experimental and theoretical methods. It was observed for the first time that fine η-(Fe, Cr)2C carbides precipitated from the martensite matrix in water-quenched high chromium cast iron during natural room temperature aging, which led to a remarkable hardness increase (by 3.4 HRC). On one hand, the obvious hardness increase was attributed to the fine precipitation of M2C carbides which was observed by transmission electron microscopy. On the other hand, it is also caused by high Cr content in the η-(Fe, Cr)2C carbides, which was confirmed by first-principles calculations.

Room-temperature aging and low-temperature experiments of ferromagnetic Sb/Sb2O3 composite nanoparticles

Sb/Sb2O3 composite nanoparticles ranging in average particle sizes from 57 to 665 nm have been prepared by levitation-jet aerosol synthesis through condensation of the antimony vapor in a mixed flow of an inert gas and oxygen. XRD established the presence of rhombohedral Sb and cubic Sb2O3 crystallographic phases in the nanoparticles. At the first time, it was established, that these nanoparticles exhibit a ferromagnetic behavior. The maximum total magnetization observed in the nanoparticles achieved 0.053 emu/g. An excess paramagnetic susceptibility has also been observed. After a long time of room-temperature aging, the susceptibility decreases, accompany by enhancement in the saturation magnetization. It was established, that a difference between the magnetic contributions at low-temperature (liquid nitrogen) and room temperature alters, depending on the average sizes of NPs. Supposedly, the presence of definite localized states in the Sb/Sb2O3 interfaces on the surface of the nanoparticles, and its mutual interactions, are responsible for the observed magnetic phenomena.

Long-life in-situ temperature field monitoring using Fiber Bragg grating sensors in electromagnetic launch high-rate hardcase lithium-ion battery

High-rate hardcase lithium-ion batteries used in electromagnetic launch(EML) applications operate under continuous high-current pulse conditions, accompanied by intense heat generation and large internal temperature gradients. Accurate detection of the characteristics of their internal temperature field is difficult using conventional temperature measurement methods, which in turn causes difficulties in defining their safe-use boundaries. In this paper, we proposed a method for embedding long-life optical fiber grating temperature sensors inside a high-rate hardcase lithium-ion battery to achieve long-period in-situ detection of the temperature field inside the battery. The room temperature aging study and constant current charge/discharge results showed no significant difference in performance between the two sensors-embedded batteries and the same batch of battery after 20 months of preparation. The temperature calibration results showed that the relative error of temperature measurement of the ten embedded fiber grating temperature sensors did not exceed 0.5 K at all 3 stages. This test data can guide optimal design and guarantee the ultimate safe use of the high-rate battery.

(Europe Section Heinz Gerischer Award) The Long Reach of Electrochemistry: Semiconductors, Metallization and Energy Storage

Research in several different areas over the past half-century is briefly reviewed with some discussion on the evolution of equipment and techniques. Examples from our work on oxygen evolution on ruthenium and iridium and electrochromism in anodic iridium oxides in the 1970s and on lithium batteries in the 1980s are discussed. Topics in the science and technology of compound semiconductors range from epitaxial crystal growth to electrochemistry and nanopore formation. Some results are presented on electrodeposition of copper metallization including in-situ stress measurements and atomic force microscopy during deposition, and spontaneous morphology changes during room-temperature aging. Electrochemical kinetics of vanadium redox reactions on carbon electrodes is discussed as well as state-of-charge monitoring and thermal stability of the positive electrode in vanadium flow batteries.

Ultrastable metallic glass by room temperature aging

Glasses have markedly different stability around their glass transition temperature (Tg), and metallic glasses (MGs) are conventionally regarded as metastable compared to other glasses such as silicate glass or amber. Here, we show an aging experiment on a Ce-based MG around its Tg (~0.85Tg) for more than 17 years. We find that the MG with strong fragility could transform into kinetic and thermodynamic hyperstable state after the long-term room temperature aging and exhibits strong resistance against crystallization. The achieved hyperstable state is closer to the ideal glass state compared with that of other MGs and similar to that of the million-year-aged amber, which is attributed to its strong fragility and strong resistance against nucleation. It is also observed through the asymmetrical approaching experiment that the hyperaged Ce-based MG can reach equilibrium liquid state below Tg without crystallization, which supports the idea that nucleation only occurs after the completion of enthalpy relaxation.

Effects of cryorolling, room temperature rolling and aging treatment on mechanical and corrosion properties of 7050 aluminum alloy

In this study, effects of cryorolling (CR), room temperature rolling (RTR) and subsequent aging treatment on mechanical and corrosion properties of 7050 aluminum alloy (AA7050) were investigated. After the severe rolling deformation, the ultrafine-grained structure and high-density dislocations are produced in CR and RTR AA7050 alloys. CR AA7050 exhibits higher volume fraction of UFGs and dislocation density compared to RTR AA7050. Both CR and RTR AA7050 alloys follow the precipitation procedure of nucleation, growth and coarsening, while the DSC test shows that CR AA7050 has stronger response to aging treatment and age-hardening effect. CR AA7050 presents higher micro-hardness (253 HV), yield strength (650 MPa) and ultimate tensile strength (685 MPa), while the elongation (2.2%) is less than RTR AA7050 (245 HV, 573 MPa, 613 MPa, 3.5%). The aging treatment can improve the elongation of rolled samples, while the other mechanical properties are gradually decreased with the increasing in aging time. CR and RTR AA7050 sheets show a low corrosion resistance, while CR are beneficial to improving the corrosion resistance of the aged samples.