Low-temperature Behavior Research Articles

Low-temperature oxidation behaviors of Cu-15Ni-8Sn alloy in different aging conditions

Cu-15Ni-8Sn (wt%) alloy has been widely used in engineering applications due to its excellent mechanical strength, wear, and corrosion resistance. However, low-temperature oxidation (LTO) poses a significant challenge, restricting its further application and longevity. In this study, the low-temperature oxidation behavior of the Cu-15Ni-8Sn alloy under different aging condition was investigated using multi-scale characterization by SEM and TEM. The characterization results reveal the oxide films of the aged sample contain tri-layers at low temperature, the outermost layer is dominated by CuO and Cu2O, the middle oxide layer contains of Cu2O, NiO, SnO2 and SnO, and the inner oxide layer is composed of NiO and SnO2. In addition, the as-quenched sample has superior oxidation resistance compared to the aged samples, and the oxidation resistance of the aged samples decreases with the increase of aging time. That is, there is a trade-off between hardness and oxidation resistance in aged Cu-15Ni-8Sn alloys. Therefore, these findings provided a way to adjust the aging parameter based on specific service conditions.

Enhancing of low-temperature deformation compatibility of pure titanium welded tube by laser welding and cold-worked in welded zone

This study is aimed to improve the low-temperature deformation behaviour of titanium heat exchange tubes by optimizing welding method and weld treatment processes. The various welding processes and cold-worked in welded zone process are adopted, and the effects of macro-morphology, microstructure and mechanical properties on low-temperature deformation behaviour are studied. The results show that the width of the laser welded joint and welded zone is 3.8 mm and 2.9 mm respectively, which is 40% and 63% of TIG welded joint. Especially, the width of heat affected zone and the grain size of laser welded joint are obviously reduced due to its concentrated energy density. The cold-worked process in welded zone can relieve the macroscopical and microstructural discontinuity between base metal, heat affected zone and welded zone. The inner weld reinforcement is eliminated to improve smooth transition and the columnar α grains in welded zone are remarkable fragmented with plenty of twins. The hardness of the welded zone after cold-worked is significantly higher than that of the base metal, resulting in base metal being the main deformation area of the welded tube at low temperature, which is beneficial to improve the deformation performance of the whole welded tube. By adapting the cold-worked and laser welding process with smooth transition and narrower weld width, the pure titanium welded tube can meet the requirement of three times low-temperature deformations.

Analysis of Factors Influencing the Low-Temperature Behavior of Recycled Asphalt Mixtures in Seasonal Freeze-Thaw Regions

Analysis of Factors Influencing the Low-Temperature Behavior of Recycled Asphalt Mixtures in Seasonal Freeze-Thaw Regions

In-situ cryogenic X-ray diffraction analysis of Poly(dimethylsiloxane) oil and film

Understanding the phase transitions and crystallographic characteristics of polysiloxane materials poses a significant challenge. To address this issue, a custom cryogenic chamber has been developed and integrated with a laboratory X-ray diffraction apparatus, enabling the execution of in-situ temperature-dependent X-ray diffraction (XRD) analyses across the cooling and heating cycles. Through the utilization of diverse sample holders, the real-time monitoring of crystallization and melting phenomena in both linear poly(dimethylsiloxane) (PDMS) oil and crosslinked PDMS film has been made feasible. Notably, high-quality X-ray diffraction data, encompassing 13 diffraction lines, are successfully acquired for the first time for linear PDMS oil at 153K. Subsequent crystallographic examination has revealed a tetragonal unit cell characterized by lattice parameters a = b = 8.3379 Å, c = 11.9284 Å, and space group I 41, suggesting the adoption of a fourfold helical conformation by two polymer chains, each comprising four monomer units, within the lattice structure. This improved and versatile X-ray instrumentation presents clear advantages over conventional commercial powder X-ray diffractometers, which is anticipated to provide a promising in-situ characterization approach for investigating the low-temperature behaviors of liquid or oil materials.

Leveraging Ion Pairing and Transport in Localized High-Concentration Electrolytes for Reversible Lithium Metal Anodes at Low Temperatures.

Coulombic efficiency of over 99% is rarely achieved for Li metal anode below -40°C, hindering the practical application of high-energy-density Li metal batteries under extreme conditions. Herein, limiting factors for Li metal reversibility are investigated utilizing ether-based localized high-concentration electrolytes of different solvent-diluent combinations. We find that along with the desolvation barrier, bulk ion transport properties including ionic conductivity, transference number, and diffusivity are also crucial factors for low-temperature Li deposition behavior. Superior Li metal reversibility was observed within the combination of the solvent with moderately weak solvating power and the diluent with minimal viscosity, highlighting the role of ion transport and the necessity for a trade-off with desolvation. The optimized electrolyte composed of lithium bis(fluorosulfonyl)imide, methyl n-propyl ether, and 1,1,2,2-tetrafluoroethyl methyl ether delivers exceptional Coulombic efficiency of 99.34% at -40°C and 98.96% at -60°C under a current density of 0.5 mA cm-2. Furthermore, Li||LiCoO2 (2.7 mAh cm-2) cells demonstrate impressive reversible capacity and cycling stability at these temperatures. This work sheds light on the less-recognized relevance of bulk ion transport to low-temperature performance and provides guidelines for the electrolyte design of Li metal batteries operating in cold environments.

Structural distortion-induced low-temperature dielectric dispersion in lanthanide titanate pyrochlores

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials.

Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe4 Particles.

NbTe4 is an important material because of its fundamental low-temperature electronic behavior and its potential interest for thermoelectric, catalytic, and phase-change applications, especially as nano- and microscale particles. As a tellurium-rich group V transition metal telluride, bulk NbTe4 is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe4 films can be made by sputtering and annealing, but NbTe4 is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe4 particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situ through a multistep pathway that begins by first forming elemental tellurium needles. NbTe4 then deposits on the surface of the tellurium needles through a diffusion-based process. Time-point studies throughout the reaction reveal that crystallographic relationships between Te and NbTe4 define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe4 particles. As synthesized, NbTe4 particles exhibit a surface consisting of predominantly Nb-Te and reduced NbOx species, but after storage, surface oxidation transforms these species to primarily Nb2O5 and TeO2, while the NbTe4 remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe4, made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.

Low-temperature oxidation behavior and mechanism of hot-dip Al and Al[sbnd]Si coatings on Mo substrate at 600 °C in static air

The hot-dip Al and AlSi coatings are synthesized on Mo substrate at different temperatures. The microstructure and low-temperature oxidation behavior both of the coatings are investigated. The results indicate that hot-dip Al coating is mainly made up of an Al4Mo outer layer and an Al8Mo3 interface layer, while the hot-dip AlSi coating is consists of a Mo(Si, Al)2 inner layer and AlSi alloy outer layer containing Mo(Si, Al)2 grains. After exposed at 600 °C for 40 h, a large number of cracks initiate on surface and inside of the hot-dip Al coating, its mass gain per unit area (Δm) reach to 10.32 mg/cm2, and the RSa (average surface roughness) and Sdr (surface area growth rate) values increase from 0.216 μm and 6.602% before oxidation to 1.214 μm and 35.297%, respectively. During the oxidation process, the structure of the hot-dip AlSi coating is preserved intact, and almost no cracks are observed in the coating. After oxidized at 600 °C for 150 h, the Δm of hot-dip AlSi coating is only 1.56 mg/cm2, and the RSa and Sdr values increase from 0.458 μm and 7.083% to 1.509 μm and 43.586%, respectively. Besides, the oxidation rate constant (Kp) of hot-dip Al and AlSi coatings are 7.42 × 10−4 and 4.47 × 10−6 mg2·cm−4·s−1, respectively, and the latter is only 6.17 × 10−3 times than that of the former. The excellent oxidation resistance of hot-dip AlSi coating is attributed to its small grain size, stable and dense coating structure, and complex oxide layer composition.

Unusual low-temperature behavior in the half-filled band of the one-dimensional extended Hubbard model in atomic limit.

Recently, a kind of finite-temperature pseudotransition was observed in several quasi-one-dimensional models. In this work, we consider a genuine one-dimensional extended Hubbard model in the atomic limit, influenced by an external magnetic field and with the arbitrary number of particles controlled by the chemical potential. The one-dimensional extended Hubbard model in the atomic limit was initially studied in the seventies and has been investigated over the past decades, but it still surprises us today with its fascinating properties. We rigorously analyze its low-temperature behavior using the transfer matrix technique and provide accurate numerical results. Our analysis confirms that there is an anomalous behavior in the half-filled band, specifically occurring between the alternating pair (AP) and paramagnetic (PM) phases at zero temperature. Previous investigations did not deeply identify this anomalous behavior, maybe due to the numerical simplicity of the model, but from an analytical point of view this is not so easy to manipulate algebraically because one needs to solve an algebraic cubic equation. In this study, we explore this behavior and clearly distinguish the pseudotransition, which could easily be mistaken with a real phase transition. This anomalous behavior mimics features of both first- and second-order phase transitions. However, due to its nature, we cannot expect a finite-temperature phase transition in this model.

Numerical studies on low-temperature eccentric-compression behaviours of UHPC-filled Q690E high-strength steel tubes

This paper numerically studied the compression behaviours of ultra-high performance concrete - filled square high strength steel tubes (UFSHTs) at low temperatures. Firstly, finite element models (FEMs) were developed to simulate the ultimate strength behaviours of UFSHTs under bending and compression, which were extensively validated by bending and compression test results. Then, extensive FEM analysis were carried out to investigate the low-temperature eccentric-compression behaviours of UFSHTs at low temperatures. The studied parameters in this numerical analysis included low temperatures, eccentricities, and slenderness ratios. The FEM parametric studies showed that (1) reducing low temperatures improved the eccentric-compression capacities; (2) The load-displacement curves exhibited a more protracted hardening stage with higher eccentricity ratios; (3) the normalized N-M curves were shrunk inward with slenderness ratios increasing. Finally, modified code equations were proposed to estimate the N-M interactions of UFSHTs under low-temperature eccentric-compressions, and validations of the predictions against the test and numerical results confirmed that the modified Eurocode 4 code equations provided more reasonable estimations than AISC360 and GB50936.

Synergistic effects of aggregate-void distribution on low-temperature fracture performance and crack propagation of asphalt concrete under mode I and mode II fracturing

Mesoscopic structures of asphalt concrete play an important role in low-temperature cracking behavior. Existing studies mainly focus on a single feature of the mesoscopic structure, neglecting the spatial distribution and synergistic effects of aggregates and voids, especially in Mode II fracturing. The results show that: in the case of −5 °C and Mode I fracturing, the fracture trend is less affected by the spatial distribution of mesoscopic structure, and tending to spread through aggregate and asphalt mastic along the shortest path. In the case of −5 °C and Mode II fracturing, the crack is easily affected by the distribution of large particle size aggregates in the initial zone, but not by the uneven distribution of voids. In the case of 10 °C and Mode I fracturing, the dominant large aggregate particle size influence on the path is weakened, and the effect of void distribution on the cracking path is perceptibly increased. In the case of 10 °C and Mode II fracturing, the location of large-particle aggregate determines the main streak of fractures, and the uneven distribution of void space determines the occurrence of fracture bending.

Low-Temperature Nucleation Behavior of L12 Al3Zr Precipitates in a Dilute Al-Zr-Sn Alloy

Low-Temperature Nucleation Behavior of L12 Al3Zr Precipitates in a Dilute Al-Zr-Sn Alloy

Cathodoluminescence studies of the optical properties of a zincblende InGaN/GaN single quantum well

Zincblende GaN has the potential to improve the efficiency of green- and amber-emitting nitride light emitting diodes due to the absence of internal polarisation fields. However, high densities of stacking faults are found in current zincblende GaN structures. This study presents a cathodoluminescence spectroscopy investigation into the low-temperature optical behaviour of a zincblende GaN/InGaN single quantum well structure. In panchromatic cathodoluminescence maps, stacking faults are observed as dark stripes, and are associated with non-radiative recombination centres. Furthermore, power dependent studies were performed to address whether the zincblende single quantum well exhibited a reduction in emission efficiency at higher carrier densities—the phenomenon known as efficiency droop. The single quantum well structure was observed to exhibit droop, and regions with high densities of stacking faults were seen to exacerbate this phenomenon. Overall, this study suggests that achieving efficient emission from zinc-blende GaN/InGaN quantum wells will require reduction in the stacking fault density.

Acetamide-based deep eutectic solvents as efficient electrolytes for K–MnHCFe//Zn dual-ion batteries

In this study, a cost-effective, eco-friendly deep eutectic solvent (DES), comprising acetamide, sodium perchlorate, and zinc chloride serves as an innovative electrolyte for dual ion batteries. Notably, the DES exhibits a broad electrochemical stability window, self-extinguishing behavior, and great resilience in low temperatures. The interplay between the electrolyte components is being thoroughly scrutinized, with a particular focus on the benefits of adding a co-solvent to the DES. This addition prevents unwanted reactions and zinc dendrite growth through the formation of a solid electrolyte interphase (SEI) layer, ultimately leading to enhanced coulombic efficiency and cyclic stability. The electrochemical performance of zinc ion batteries (ZIBs) using a Prussian blue analog (K–MnHCFe) as cathode is being examined in the dual-ion DES electrolyte. The device displays a discharge capacity of 76.4 mAh g−1 at 0.3 A g−1 and a maximum energy density of 111.7 Wh kg−1 at a power density of 437.5 W kg−1. Furthermore, it retains 65 % of its initial specific capacity even after 3000 cycles at 0.5 A g−1. It is noteworthy that the ZIB device with dual-ion DES operates normally in temperatures as low as −20 °C, outperforming traditional cells with aqueous electrolytes.

Low-Temperature Mechanical Behavior of Fe-SMA for Structural Damping

Low-Temperature Mechanical Behavior of Fe-SMA for Structural Damping

Investigation of Rutting and Low Temperature Cracking Behavior of Reactive Ethylene Terpolymer and Waste Cooking Oil Modified Bitumen

With sustainability being the most crucial issue of recent years, the use of waste materials in bitumen modification is increasing and becoming widespread. In this experimental study, it was aimed to investigate the high- and low-temperature behavior of bitumen samples modified with waste cooking oil (WCO), reactive ethylene terpolymer (RET), and polyphosphoric acid (PPA). Accordingly, the multiple stress creep and recovery (MSCR) test and the bending beam rheometer (BBR) test were conducted. Depending on the increasing WCO ratio, the Jnr,R%,∆T_c,and λ parameters of modified bitumens were examined in detail. It was observed that with increasing WCO ratio,the Jnr value increased, and elastic recovery and stiffness decreased. In addition, it has been determined that this composite-modified bitumen is resistant to heavy traffic loads and has sufficient flexibility at low temperatures.

An in-depth exploration of the impact of novel collector HPDDA on the low-temperature flotation behavior of bastnaesite and quantum chemical calculation

Traditional cationic collectors commonly suffer from drawbacks such as poor solubility and low-temperature resistance, which impede the effectiveness of flotation. Hence, this study designed and synthesised a novel collectors, 2-Hydroxypropane-1,3-bis(dodecyl dimethyl ammonium) bromide (HPDDA), tailored for low-temperature flotation of bastnaesite. The positive charges of the surface molecular electrostatic potential (ESP) of HPDDA concentrate near the two quaternary ammonium groups, with minimal points also appearing between the two N atoms. Near the quaternary ammonium groups, weak van der Waals (vdW) and spatial hindrance occur due to the abundance of polar groups. The Krafft point test reveal that the Krafft point of HPDDA was below 0 °C, significantly higher than that of DDA. HPDDA exhibited excellent pH adaptability and cold resistance, demonstrating outstanding selective capturing capability for bastnaesite even at low temperatures, thereby enabling the separation of bastnaesite from calcite. Analysis through various detection methods such as zeta potential, Fourier transform infrared (FT-IR), contact angle measurement, and X-ray photoelectron spectroscopy (XPS) elucidates the selective adsorption mechanism of HPDDA on the surface of bastnaesite, attributing it to the differences in surface electrification and other properties between bastnaesite and calcite. This work provides new collector and theoretical guidance for solving the low-temperature flotation of bastnaesite.

Local detailed balance for active particle models

Starting from a Huxley-type model for an agitated vibrational mode, we propose an embedding of standard active particle models in terms of two-temperature processes. One temperature refers to an ambient thermal bath, and the other temperature effectively describes ‘hot spots,’ i.e. systems with few degrees of freedom showing important population homogenization or even inversion of energy levels as a result of activation. That setup admits to quantitatively specifying the resulting nonequilibrium driving, rendering local detailed balance to active particle models, and making easy contact with thermodynamic features. In addition, we observe that the shape transition in the steady low-temperature behavior of run-and-tumble particles (with the interesting emergence of edge states at high persistence) is stable and occurs for all temperature differences, including close to equilibrium.

Revealing the low-temperature friction behavior and mechanisms of hydrogenated amorphous carbon films with Al/Cr/Si doping

Hydrogenated amorphous carbon (a-C:H) film has emerged as a significant contender for solid lubrication applications in low-temperature environments. Here, a set of a-C:H films doped with varying contents of elements (Al, Cr, Si) (AlCrSi/a-C:H) were fabricated, and their low-temperature frictional evolution pattern and mechanisms were explored. The results revealed that the films maintained a superlubricity state as the temperature decreased to − 40 °C, and when the temperature further decreased, the coefficient of friction increased followed by a significant fluctuation. It was related to the competition between shear graphitization, abrasive wear, transfer film formation, and film embrittlement in different low temperature ranges. This work provides new evidence for understanding the carbon film low-temperature friction behavior.

Thermal conductivity of nonunitary triplet superconductors: application to UTe2

Considerable evidence shows that the heavy fermion material UTe2 is a spin-triplet superconductor, possibly manifesting time-reversal symmetry breaking, as measured by Kerr effect below the critical temperature, in some samples. Such signals can arise due to a chiral orbital state or possible nonunitary pairing. Although experiments at low temperatures appear to be consistent with point nodes in the spectral gap, the detailed form of the order parameter and even the nodal positions are not yet determined. Thermal conductivity measurements can extend to quite low temperatures, and varying the heat current direction should be able to provide information on the order parameter structure. Here, we derive a general expression for the thermal conductivity of a spin-triplet superconductor and use it to compare the low-temperature behavior of various states proposed for UTe2.